watermakers for sailboats

• BOAT OF THE YEAR
• Newsletters
• Sailboat Reviews
• Boating Safety
• Sailing Totem
• Charter Resources
• Destinations
• Galley Recipes
• Living Aboard
• Sails and Rigging
• Maintenance
• Best Marine Electronics & Technology

Do You Need a Watermaker for Your Sailboat?

• By Jen Brett
• Updated: October 2, 2019

I remember, in the not too distant past, when having a watermaker aboard a cruising boat seemed to be the ultimate luxury. Plenty of sailors considered them too expensive and complicated. Fortunately times have changed. With improved technology and a range of price points on the market, now even average cruising boats of modest means carry a reverse-osmosis system. And really, is there anything that feels better after a day spent sailing and swimming than a hot shower? The freedom and security that come with full water tanks are also a nice bonus, particularly if you’re cruising in an area where fresh water is difficult to come by and pricey when you do.

Choosing a Watermaker

As with any major system, there are many factors to consider when you choose a watermaker. You’ll need to figure out your freshwater needs, the space you have available for the system and how you’re going to power it . Generally speaking, in a reverse-osmosis desalination system the raw water is run through a series of pre-filters, and then a high-pressure pump moves the water through one or more membrane housings. The wastewater, or brine, is released overboard and the product water goes into your water tanks.

Since all of the watermakers that are currently available for cruising sailboats use this process for desalination, the major differences between the systems are how you power the high-pressure pump and the user interface. Powering options include 120/220-volt AC, 12- or 24-volt DC and engine/belt driven. All have their pros and cons.

“The first question I ask a potential customer is ‘Will your boat have a ship’s generator?’” said Rich Boren of Cruise RO Water. “If they plan to have a generator, then the decision to go with a 120-volt high-output watermaker seems natural. While running the generator for battery charging and other loads two to three times per week, they can keep their water tanks full without having to make generator runs just to make water.”

A 12-volt system, such as the Spectra Catalina 300 Mk II or the Horizon Reverse Osmosis Seafari Quest, makes a lot of sense for smaller cruising boats since they don’t need a generator to run and have fairly miserly power consumption. On a breezy, sunny day, a solar panel and/or a wind generator will likely keep up with the demand. “The only difference between 12-volt DC low-output and 120-volt AC high-output watermakers is how the high-pressure pump brings seawater up to the 800 psi needed to drive fresh water through the reverse-osmosis membrane,” Boren said. “The membrane and support equipment, like pre-filtering and plumbing, are the same.”

These systems typically produce anywhere from about 6 to 16 gallons per hour, and some units can do so for about a 1-amp-per-gallon power draw.

“Many smaller sailboats, under 45 feet or so, often utilize solar panels,” said Berkeley Andrews of Parker Hannifin, which produces Sea Recovery, Horizon Reverse Osmosis and Village Marine watermaker systems. “Their entire electrical backbone consists of 12-volt or 24-volt. So they must have a watermaker that can operate on low voltage. These customers have limited amp hours on their batteries, so all of their equipment must be suited to handling this.”

In choosing a watermaker, Bill Edinger, owner of Spectra Watermakers, said to be realistic about water needs. “When helping customers decide which system is right for them, first we like to determine their approximate water usage with questions like ‘How many people are aboard normally? Are you going to be living on the boat full time? Do you have a washing machine? Any children? Are you going to be cruising full time or leaving the boat for extended periods?”

A common error people make is choosing a watermaker that is too small for their needs. “The most common mistake I see cruisers making in their watermaker purchase decision is underestimating how much water it will take them to cruise comfortably,” Boren says. “I’m not talking about the minimal amount of water it takes for the crew to stay alive, because there is a big difference between staying alive and comfort. Selecting a watermaker that will only meet their minimal drinking-water needs but not keep up with the comfort needs of the crew can lead to crew tensions and feeling like camping rather than cruising.”

Remember that “watermakers are rated in gallons of production in a 24-hour period,” Edinger said. “So a 300-gallon-per-day watermaker system sounds like a lot of water. The important thing is that it produces about 12 gallons per hour. Normally a system like this will be run three to four hours per day if power is not a critical issue, in this case producing 36 to 48 gallons of water. It’s better for a system to run for a few hours every few days than an hour every day.”

Watermakers for Small Boats

If space is at a premium, consider purchasing a modular system instead of an enclosed one. In a modular system, the components, such as the membranes and filters, can be mounted separately. Another power source for the high-pressure pump is the boat’s diesel engine. In these engine-driven setups , the pump and an additional pulley are mounted on a custom bracket next to the engine. The watermaker can then be run while motoring or using the engine to charge the batteries.

While engine-driven watermakers can produce a large amount of water, 20 or more gallons an hour on average, the downside is that the installation can be more complex than for other systems. “Unlike the 12-volt DC or 120-volt AC watermakers, where you simply bolt the high-pressure pump down and then run the wires and plumbing hoses, the hardest installation aspect of an engine-driven watermaker is finding space. Some boats simply have no room in the engine compartment to mount the 5-pound pump with a 7-inch pulley on the engine while still leaving access to other engine parts that need to remain serviceable,” Boren says.

A relative newcomer to the marine market, the portable watermaker is a good solution for cruisers who want the convenience of a watermaker but don’t want to permanently install one. The Rainman is one such system that is available as a self-contained unit driven by a gasoline-powered Honda motor, or as a 115-volt AC-powered unit. “The bulk of our gasoline-powered system customers are sailing yachts between 30 and 50 feet,” said Ron Schroeder of Rainman Desalination. “Our customers seem to prefer to have a simple and somewhat manual system over one that relies on control panels, software and solenoid valves. We are also attractive to those customers who have had bad experiences with the installation process of an installed system.”

The Spectra Passport is another portable system. Edinger said it has already proved popular with offshore race crews and cruisers who need a watermaker for only a limited time.

Maintenance for Watermakers

Watermakers have long had a reputation for being difficult to maintain, but the equipment has improved over the years and overall, routine maintenance isn’t more challenging than with other onboard systems. “The best rule of thumb is to operate the watermaker in water that looks good,” Andrews said. “There are a few factors in the feed-water condition that come into play. Operating a watermaker in dirty harbors will most certainly result in repeated pre-filter changes and a clogged sea strainer. If you have extra filters on board, you can get by, but it’s not recommended. The environment in the open ocean and remote anchorages is much better. Also consider how shallow the water is where you’re anchored. Sometimes there can be a lot of tidal movement, which can kick up fine particulate and sediment. This too can also contribute to more frequent filter changes and even damage other components. A nice option is an automatic freshwater flush, which will rinse the watermaker’s membrane element after use. It helps keep the membrane vessel housing free of any biological growth that could foul the membrane and reduce your ability to produce fresh water.”

Whatever system you choose, with proper use and maintenance you can expect years of service from your watermaker. And plenty of hot showers.

Jen Brett is a CW associate editor. This article first appeared in the February 2015 issue of Cruising World.

Aqua Marine: www.aquamarineinc.net

Blue Water Desalination: www.bluewa​terdesalination.com

Cruise RO: www.cruiserowaterandpower.com

Dometic Marine Sea Xchange: www.do​metic.com

ECHOTec: www.echotecwatermakers.com

FCI Watermakers: www.filtrationconcepts.com

Horizon Reverse Osmosis (HRO): www.hrosystems.com

Katadyn: www.katadyn.com

Rainman: www.rainmandesal.com

Sea Recovery: www.searecovery.com

Schenker Watermakers: www.schenkerwa​termakers.com

SK Watermakers: www.skwatermakers.net

Spectra Watermakers: www.spectrawater​makers.com

Village Marine Tec: www.villagemarine.com

Watermakers Inc.: www.watermakers.com

• More: DIY Sailboat Projects , How To , systems
• More How To

3 Clutch Sails For Peak Performance

It’s Time to Rethink Your Ditch Kit

8 Ways to Prevent Seasickness

How To De-Winterize Your Diesel Engine

The Moorings Expands in Croatia

C-Map Updates North America Charts

New to the Fleet: Italia Yachts 12.98

St. Vincent Court Orders Deportation For Hijacking Suspects

• Digital Edition
• Customer Service
• Privacy Policy
• Terms of Use
• Email Newsletters
• Cruising World
• Florida Travel + Life
• Sailing World
• Salt Water Sportsman
• Sport Fishing
• Wakeboarding

Many products featured on this site were editorially chosen. Cruising World may receive financial compensation for products purchased through this site.

Copyright © 2024 Cruising World. A Bonnier LLC Company . All rights reserved. Reproduction in whole or in part without permission is prohibited.

Home » Blog » Gear » Watermakers: a guide to marine desalinators and making water on a boat

Watermakers: a guide to marine desalinators and making water on a boat

By Author Fiona McGlynn

Posted on Last updated: March 23, 2022

There’s something magical about a watermaker—at least that’s how I felt after we installed one on our boat. That may sound overblown, but think about it: watermakers transform salt water into fresh water, providing a near-endless supply of potable water for drinking, bathing, and cleaning! THAT my friends is an amazing piece of technology!

(If you don’t share my enthusiasm, try going without a shower for a few days and you’ll begin to see my point).

Having experienced living on a boat and cruising, both with and without a marine desalinator, I can attest that it’s a game-changing piece of gear. However, you definitely don’t need one to go cruising. There are plenty of low-tech ways to collect and make water on a boat.

Marine desalinators do offer some major benefits: there’s more water for showers, it’s easier to travel farther afield, you can spend more time in a remote location. However, these benefits have to be weighed against the drawbacks: namely a hefty price tag and ongoing maintenance.

Deciding whether a watermaker is right for you will come down to the type of cruising you’re doing, how much water you need, and your budget. Read on to learn about the pros and cons, costs, and key features of marine watermakers.

Table of contents

• 1 How does a watermaker work?
• 2.1 Benefits
• 2.2 Drawbacks
• 3.1 Powered or handpump
• 3.2 Electric or engine drive
• 3.3 Energy recovery watermaker
• 3.4 Modular, self-contained, and portable watermakers
• 3.5 Automatic flushing systems
• 3.6 Automatic Pressure Regulation and adjustable pump speed
• 3.7 Remote control panels
• 4 Top watermaker brands

How does a watermaker work?

A watermaker on a yacht converts seawater into fresh water through a process known as reverse osmosis (RO). A high-pressure pump pushes seawater through a semi-permeable membrane that filters out salt, organics, and bacteria. The fresh water is pumped into your water tanks while the remaining brine bi-product is discharged over the side of the boat, back into the ocean.

Marine watermakers: the benefits and drawbacks

Less water rationing.

When we started our 13,000 mile trip across the Pacific, we didn’t have a watermaker. We were on a tight budget and decided to prioritize other pieces of equipment like a life raft and wind vane.

As a result, we became experts in conserving water on a boat . We would carefully ration out water for washing dishes, taking showers, and even brushing our teeth!

After getting a watermaker we became far less meiserly because we knew we could always make more water if we needed to. It was a relief to not be constantly thinking about how much water we were using over the course of a day.

That being said, we couldn’t relax completely. We had to keep our tanks topped up, so as not to run the pump dry. We also always carried potable water in reserve, in case our watermaker broke in the middle of a long passage.

More luxuries

Can’t live without a proper shower? A boat water maker can make water-intensive luxuries like freshwater deck washdown, freshwater flushing heads, laundry, daily showers, and even baths, a possibility.

As great as this sounds in theory, we were surprised to find that we didn’t indulge in more showers after we got the watermaker.

We continued to use a hand pump pesticide sprayer to shower on deck despite having a watermaker and shower below. While some of this came down to habit, we also disliked running our engine (and consuming diesel) just to run the watermaker.

No hauling water

For us, this was by far the greatest benefit of having a watermaker!

While cruising in the US and Canada, we could refill our water tanks at a dock or marina. This was a minor hassle because it involved pulling up the anchor and docking the boat.

In Mexico, it was more challenging to get water. We would fill 5-gallon jugs at the local water purification plant in town and wheel them back to our boat on a collapsible dolly.

It often took a couple of trips with the dolly and dinghy to fill our water tanks. Oh, and we broke our dolly, twice!

We realized that if we wanted to spend more time exploring, and less time hauling water, we would have to invest in a watermaker. When we reached La Paz, Mexico we bought a refurbished watermaker, and we were so glad we did!

Our sailboat water maker gave us the gift of time, especially in places like Mexico and the South Pacific, where there were limited opportunities to fill water tanks up at the docks. It also saved us paying docking and water fees.

We estimate that our boat water maker saved us anywhere from four to six hours every week, time that we could spend exploring the wonderful places we were visiting.

A clean, safe water source

In places where the drinking water may be suspect, a boat water maker can be a reliable source of safe drinking water (assuming it’s in good working condition!).

More time in remote locations

A watermaker is a great tool if you’re drawn to remote locations where you might be the only boat in the anchorage.

It wasn’t until we reached Los Frailes, a secluded village on the Baja, that we really began to think about buying a watermaker.

There we were in an idyllic anchorage, surrounded by spectacular hiking and fishing. There was only one problem—every two days we had to walk 10 miles into town with our water jugs and hope that some kind samaritan would give us a lift back to our boat.

Before having a watermaker, we’d often leave a place we loved just because we needed to fill up our tanks. With a watermaker, we were more self-sufficient and could stay an extra few days, or as long as we wanted!

The number one drawback is the cost. We were able to find a refurbished water desalinator for $3,000, which was a great deal but also a considerable slice out of our cruising kitty.

How much does a watermaker cost?

Powered desalination systems for your average recreational cruising boat range from around 3,500 USD to 11,000 USD, with the more expensive options offering higher production (gallons of fresh water per hour).

Ongoing maintenance

Watermakers are yet another piece of boat equipment that needs to be maintained.

The majority of watermaker problems are caused by not using it enough or not using it properly.

If a watermaker is not used for a few weeks, the planktonic organisms in the seawater will die, rot, and clog the membrane and filters. This can eventually damage the reverse osmosis membrane in the watermaker.

For this reason, boat water makers should be used frequently and regularly flushed with fresh water.

Watermaker flushing

Check your manufacturer’s instructions on how to flush.

Rainman recommends flushing the seawater out of the system with fresh water if you are not using the system for more than a day or two. After another week, you need to freshwater flush the system again or pickle it for long-term storage.

Of course, it’s easy to forget, so we made it a rule to freshwater flush our watermaker after every use.

This is one good reason to choose a watermaker with an output that will meet your water consumption needs but not exceed them. If you’re using it every second day, you won’t have to try and remember whether you’ve flushed it or not.

Flushing a watermaker is relatively simple but it does involve a bit of work. We used a system with buckets of fresh water to flush our system and it generally took about 5 minutes.

You can also buy systems that automatically flush your watermaker at pre-determined times—even when you’re away from the boat (more on autoflush systems below).

Whatever you do, don’t use chlorinated water to flush as it will destroy reverse osmosis membranes. It’s possible to buy a carbon filter to remove chlorine from water sources at the dock.

Pickling a watermaker

If you don’t plan on using your watermaker for a while it needs to be “pickled” with a special biocide to prevent growth and buildup which could render your reverse osmosis membrane totally useless.

A watermaker should also be pickled every so often to chemically cleanse the membrane.

In addition to flushing and pickling, you will also need to clean out and replace the raw water pre-filters.

Operating costs

When properly cared for, a membrane should last five to ten years. If you don’t properly flush or pickle your watermaker, it can be a lot sooner and membranes aren’t cheap, generally costing in the range of 200-700 USD.

You’ll also need to purchase pre-filters and pickling solution, which are generally quite affordable. It’s also a good idea to carry spare parts

Power consumption

Watermakers can be real power hogs. When Practical Sailor tested a dozen DC watermakers they found they could draw anywhere from 12 to 48 watts per gallon, a huge range in efficiency!

According to Practical Sailor, “for maximum efficiency none of the systems drawing 15 amps or more should be operated without running the engine at the same time.”

We had to run our engine for hours to fill our tanks, which was annoying (and loud) when we were hanging out at anchor and also used up another finite resource—diesel fuel.

In our view, this was the single largest drawback to having a watermaker aboard.

Keep in mind that your power supply will determine what type of watermaker you buy. You may need to upgrade your electrical panels, get a generator or high-powered alternator, add solar panels, or increase battery capacity to supply the demand.

You can’t make water everywhere

While watermakers offer great flexibility and freedom, you can’t just make water in any old spot. If you make water in a polluted marina or anchorage, you’ll risk clogging up your filter. Most cruisers will head out to open water to ensure the saltwater they’re using is as clean as possible.

Key features to look for

Powered or handpump, handpump watermakers.

Handpump watermakers tend to be small and portable, the perfect thing to keep in your ditch bag in the event of an emergency. They’re less expensive than powered watermakers and produce far less water, usually around one gallon per hour.

Though I do know cruisers who have used a handpump watermaker for everyday use, they typically tend to be kept aboard for survival situations.

Powered watermakers

Powered watermakers run off your electrical supply or engine and can produce tens of gallons of water per hour. They tend to be a lot more expensive, but they’re productive enough to replenish your tanks.

Electric or engine drive

Powered watermakers can be electrically driven, by AC or DC, or run off the boat engine.

AC watermakers

AC models can produce in the range of 20-60 gph and are ideal for cruisers with an AC generator or alternator on board. They can also be used on boats with ample solar or wind sources and an inverter.

DC watermakers

DC watermaker systems typically produce in the range of 10-30 gph and are ideal for boats with solar power or 12V battery power.

Engine-driven watermakers

On an engine-driven watermaker, the high-pressure pump is belt-driven. These can produce a considerable amount of water, even on small engines. For instance, engine-driven units produce between 20-60gph, twice what a DC unit can produce.

Energy recovery watermaker

DC watermakers have become more efficient in recent years thanks to energy recovery systems (ERS). When the water leaves the watermaker it is still under pressure. ERS uses a set of valves to make use of this excess pressure to help drive the pump, which can reduce energy consumption by as much as 80 percent.

Modular, self-contained, and portable watermakers

Watermakers can be bought as modular, self-contained, and portable units. Choosing the right one may depend on your boat size and layout and whether you’re comfortable installing the watermaker yourself.

Modular units

Modular units come as several separate components that you can mount and connect yourself. This obviously offers a lot more flexibility and is particularly useful on smaller vessels where you may not have a lot of space. The downside is that these systems will take longer to install.

Self-contained units

Self-contained units arrive pre-assembled. While easier to install, they’re often bulkier and best suited to a bigger cruising sailboat with a large engine room.

Portable watermakers

Portable watermaker systems, like the Rainman watermakers, are entirely self-contained. Their compact design makes them easy to move and stow and you can completely avoid a permanent installation.

Simply put the intake and brine discharge hoses overboard, the freshwater hose in your water tank and you’ll be making water in no time.

If you race, have multiple boats, or plan on selling your boat, a portable watermaker is a great option because it can be easily moved from boat to boat.

If we were to buy another watermaker, we would probably opt for a portable one.

Automatic flushing systems

Automatic flushing systems use your boat’s freshwater supply to flush the watermaker for several minutes every few days. These systems require additional components (e.g., a timer, carbon filters, and a motorized valve) and installation but they take a lot of the maintenance out of having a watermaker onboard.

Automatic Pressure Regulation and adjustable pump speed

Your watermaker’s efficiency will be affected by the temperature and salinity of the water you’re cruising in. Cold and highly saline waters (e.g., in the high latitudes) will be more work for your watermaker, so it will take longer to purify.

Some units feature Automatic Pressure Regulation (APR) and adjustable pump speed which can help compensate for fluctuations in water temperature and salinity.

Remote control panels

Some watermakers have the option of a control panel which allows for easier access and remote control. Control panels tend to have a fairly simple interface with just a few gauges but may include a salinity sensor—so you can keep tabs on water quality—and auto-flush integration—so you can flush your watermaker with the flip of a switch.

Top watermaker brands

If you’re considering buying a watermaker for a boat, here are some of the top brands to consider.

• Cruise RO Watermaker
• Echotec watermakers
• Horizon Reverse Osmosis (HRO)
• Sea Recovery watermakers
• Schenker watermakers
• Spectra watermakers

Fiona McGlynn is an award-winning boating writer who created Waterborne as a place to learn about living aboard and traveling the world by sailboat. She has written for boating magazines including BoatUS, SAIL, Cruising World, and Good Old Boat. She’s also a contributing editor at Good Old Boat and BoatUS Magazine. In 2017, Fiona and her husband completed a 3-year, 13,000-mile voyage from Vancouver to Mexico to Australia on their 35-foot sailboat.

Terms and Conditions - Privacy Policy

• New Sailboats
• Sailboats 21-30ft
• Sailboats 31-35ft
• Sailboats 36-40ft
• Sailboats Over 40ft
• Sailboats Under 21feet
• used_sailboats
• Apps and Computer Programs
• Communications
• Fishfinders
• Handheld Electronics
• Plotters MFDS Rradar
• Wind, Speed & Depth Instruments
• Anchoring Mooring
• Running Rigging
• Sails Canvas
• Standing Rigging
• Diesel Engines
• Off Grid Energy
• Cleaning Waxing
• DIY Projects
• Repair, Tools & Materials
• Spare Parts
• Tools & Gadgets
• Cabin Comfort
• Ventilation
• Footwear Apparel
• Foul Weather Gear
• Mailport & PS Advisor
• Inside Practical Sailor Blog
• Activate My Web Access
• Reset Password
• Pay My Bill
• Customer Service

• Free Newsletter
• Give a Gift

How to Sell Your Boat

Cal 2-46: A Venerable Lapworth Design Brought Up to Date

Rhumb Lines: Show Highlights from Annapolis

Open Transom Pros and Cons

Leaping Into Lithium

The Importance of Sea State in Weather Planning

Do-it-yourself Electrical System Survey and Inspection

Install a Standalone Sounder Without Drilling

Rethinking MOB Prevention

Top-notch Wind Indicators

The Everlasting Multihull Trampoline

In Search of the Snag-free Clew

What’s Involved in Setting Up a Lithium Battery System?

Reducing Engine Room Noise

Breaking Point: What Can Go Wrong With Your Yanmar?

Mildew-resistant Caulks for Boats

Can We Trust Plastic Boat Parts?

Repairing Molded Plastics

Mailport: Marine plywood, fuel additives, through bolt options, winch handle holders

The Day Sailor’s First-Aid Kit

Choosing and Securing Seat Cushions

Cockpit Drains on Race Boats

Rhumb Lines: Livin’ the Wharf Rat Life

Resurrecting Slippery Boat Shoes

Shoe Goo’s Gift to Sailors

Tricks and Tips to Forming Do-it-yourself Rigging Terminals

Marine Toilet Maintenance Tips

Learning to Live with Plastic Boat Bits

The Ultimate Guide to Caring for Clear Plastic

• Belowdecks & Amenities
• Marine Electronics
• Systems & Propulsion

Test of Six 12-volt Watermakers

While at first blush all appear about the same size, we find important differences in output and current consumption. the spectra 180 is amazingly efficient but expensive. of the six, village marine tec's little wonder seems the most tried and true..

Last month we took an overview of the pros and cons of 12-volt watermakers. This month, we look at high-output machines from five manufacturers, ranging from systems from industry giants such as Village Marine to small shops such as SK Engineering. All of the watermakers we looked at were production models, although the Spectra 180 we tested had been re-configured to serve as a demonstration model.

As we began our market survey and field testing, we discovered that a number of other manufacturers are jumping into the fray, realizing that 12-volt watermakers constitute a small but growing segment of the market. Most notable among these new players is HRO-another industry giant-which has been promising a state-of-the-art, computer-controlled, self-contained 12-volt watermaker for more than a year. We saw the literature a year ago at the Miami Boat Show. We saw a non-operational mockup last fall at the Southampton, England boat show. We have yet to see a functional machine in the flesh.

With the assistance of Andy Cortvriend of Ocean Link, a knowledgable Portsmouth, Rhode Island, marine servicing company, we tested product output, water quality, and electrical consumption of all the watermakers. Electrical consumption was measured with a Cruising Equipment amp-hour meter, using gel cell batteries maintained at full capacity by a Heart inverter/charger between tests.

Saltwater was pulled from lower Narragansett Bay into a large storage tank maintained at a constant temperature during the tests. The waters at our Little Harbor test facility are not as clean as open ocean waters, but are closer to the reality of the watermaking most cruisers will experience. This was not a pure laboratory test with manufactured sea water of exactly the right total dissolved solids (TDS).

We then examined each machine carefully on the bench, looking for weak points, strong points, potential installation or maintenance hang-ups, and general quality of construction.

The quality of output water was tested with a TDS meter and all machines easily met standards for potability.

The real test of any watermaker is how it performs over time-not just months, but years. Because maintenance is a key factor in longevity and trouble-free operation, the owner/operator will bear a large portion of the responsibility for the long-term success of any watermaker installation.

Here are our findings.

Village Marine Little Wonder When Village Marine Tecs Little Wonder was introduced almost a decade ago, it was the first 12-volt watermaker that actually had the capacity to supply the water needs of a medium-sized cruising sailboat without almost continual running. More than 1,500 of these compact, well-made machines have been produced, and there have been virtually no changes to the design or components over the entire production run.

Both 12-volt and 24-volt models are available, with the higher voltage model producing slightly more product flow.

The standard model is totally self-contained in a well-designed package, with all components bolted to a heavy aluminum chassis, topped off with a removable aluminum cover. Mounting requires drilling through the chassis for suitable through-bolts.

The three plumbing connections-feed water, product water, and brine discharge-are pre-plumbed through one end of the case. The wiring junction box also contains connections for an optional feed water boost pump, and an internal 25-amp breaker to protect the electrics.

Although the package is tightly plumbed, there is reasonable space between components for service.

Power for the high-pressure pump is provided by a continuous-duty 1/4-hp. Pacific Scientific motor, rated at 21.5 amps at full power. The motor is connected to the high-pressure pump by a lightweight cogged belt.

The heart of the Little Wonder is its proprietary high-pressure pump, specially made by Village Marine for this machine. It features a titanium pump head with ceramic plunger-a combination which should be corrosion-proof for the life of the watermaker. All wetted parts in the pump are titanium, type 316 stainless steel, or ceramic. High-pressure plumbing and connectors are type 316 stainless.

Monitoring includes a high-pressure gauge and product flow gauge. System pressure can be adjusted if necessary using an open-end wrench, although the factory pre-set pressure of 800 psi should be correct for most watermaking situations. The pressure regulator is a high-quality regulator, rather than the more commonly seen needle-valve adjuster.

The fiberglass pressure vessel and the standard-sized 2521 membrane are both manufactured by Village Marine, although they are industry-standard in size.

In our tests, the Little Wonder produced a product flow of 5.8 gph at 13 volts, drawing 16.7 amps-about 37.4 watts per gallon. This does not include the 1-amp current draw of the small optional booster pump, which is required for above-the-waterline installations, long feed water runs, or installations containing multiple pre-filters.

The water produced by the machine we tested was very high quality. The noise level of 79 dB, with the cover removed, was louder than the two quietest machines tested, but was not loud enough to be objectionable.

The self-contained unit is 25.5″ long, 11″ wide, and 9.25″ high, and requires a slightly larger mounting space to accommodate plumbing connections and allow access for removal of fastenings holding the cover. For tight installations, a modular version is available, which does away with the mounting chassis and uses flexible high-pressure hoses rather than rigid stainless steel tubing. Obviously, installation of the modular unit requires slightly more time, but offers a lot of flexibility-very desirable in field installations aboard the typical cruising sailboat, in which locker or shelf space is at a premium.

Documentation is excellent, with a 35-page manual covering installation, operation and maintenance.

The warranty is somewhat complex. The membrane has a three year warranty, the pressure vessel a lifetime warranty, the high pressure pump a one-year warranty-although some of its internal components have only a 90-day warranty-and the electric motor 12 months. You need a flow chart to keep it straight.

The Little Wonder comes with pre-filter, three-way cleaning valve, basic plumbing connectors, and a membrane cleaning kit. You supply PVC hose, hose clamps, and the wiring connection. Options include the boost pump (standard with the modular version, $144 for the self-contained version), a three-way sampling valve ($38), a pre-plumbed fresh water flushing system ($150), hand-held salinity meter ($49), and spares kit for extended cruising ($199). For long-range cruising, all of these options are nearly essential for any properly installed watermaker.

List price of either the self-contained or modular 12-volt Little Wonder is $3,195. It is available at slight discounts through some mail-order catalogs, and there are periodic promotions at boat shows featuring special prices and thrown-in options.

Weight of the self-contained system is 63 lb. (The modular system weighs 48 lb.)

Village Marine will soon introduce a higher-output version of the Little Wonder, a 1/3-hp. watermaker in almost the same package size. Current draw, however, will be about 26 amps, requiring heavier wiring and perhaps a look at your battery capacity and charging capabilities.

Bottom Line: There are quieter 12-volt machines, more efficient ones, cheaper ones, and others that put out more water. The Little Wonder, however, has a combination of features-ease of installation, relatively low current draw, high quality components, and a 10-year track record-that is hard to beat. You can’t go wrong with this watermaker.

SK Engineering DC 150 SK Engineering is a small watermaker manufacturer based in Ft. Pierce, Florida. They do virtually no advertising, go to few boat shows, and have a very low-overhead operation geared to the Florida market. While most of their units are AC-powered, their DC 150 is a 12-volt model with a nominal output of 6 gallons per hour.

The DC 150 is powered by a 1/3-hp. continuous-duty Pacific Scientific motor rated at 26 amps. This is a larger version of the motor that powers the Village Marine Little Wonder.

The membrane is a standard 2521, and the pressure vessel appears identical to that used by Village Marine. All high-pressure fittings are type 316 stainless, as is the rigid high-pressure plumbing.

A Giant high-pressure pump provides pressure for the system. This is a standard industrial pump with a stainless steel pump head. A complete servicing manual for the pump is provided.

This is an open-frame system, with the components mounted on a heavy aluminum chassis. The footprint is 18.5″ x 12.5″, with a height of 8.5″. The pressure vessel is mounted on the outside of the chassis, increasing overall dimensions to about 25″ long outside the footprint of the mounting frame. Rubber vibration mounts are provided to isolate the chassis, reducing noise and vibration.

System pressure is user controllable via a knob-operated valve on the panel. Monitoring capabilities include system pressure and product water flow.

In operation, the DC 150 was one of the quietest machines tested, producing a maximum of 72 dB of noise. Product flow of the test machine was 6.5 gallons at 800 psi, with the motor drawing 21.3 amps at 13 volts. This translates into electrical consumption of 42.6 watts per gallon of water produced. As with other systems, adding a booster pump for above-waterline installations would add to total current draw. SK states that the system will operate without a booster pump in installations up to 2′ above the waterline.

One of the nicer features of this machine is the availability of a remote operating panel. This option allows routine operation of the system without direct access to the watermaker itself, which greatly increases installation flexibility.

The system is supplied with a pre-filter with a vacuum gauge, allowing you to monitor the condition of the filter without opening the housing. A freshwater flush kit-highly-desirable in any installation-is a $125 option. The 12-volt booster pump, drawing 1 amp, is a $120 option. An extensive cruising kit, including 12 pre-filters, rebuild parts for the high-pressure pump, cleaner, preservative, and other spares, costs $330.

SKs pricing is very competitive. The self-contained DC 150 has a list price of $2,740, but has a discount price-which we suspect would be available to most sailors who approach the manufacturer directly-of $2,350. The remote panel version has a discount price of $2,450, although the list price jumps to $3,140.

The system documentation is basic, but adequate. Total system weight is 74 lbs.

Being a small manufacturer, SK has a limited network of regular servicing dealers, but since all the system components are essentially off-the-shelf items, any good watermaker technician could repair the unit if necessary.

This is a quiet system with high-quality components and a great deal of installation flexibility when coupled with the optional 8″ x 8″ remote panel. Its open-frame design is easily serviced, although the package is not as neat as a totally enclosed package like the Little Wonder.

Bottom Line: With its 1/3-hp. motor, electrical installation will require careful thought, and you will need to look at your entire charging system and battery capacity a little more closely than you would with a 1/4-hp. machine.

The low price makes this system worth looking at. It is simple, soundly engineered, and utilizes good quality, standard components that are easily serviced. The only potential drawback is the small size of the manufacturer, which might limit long-term support.

PUR PowerSurvivor 160E The PowerSurvivor 160E is PURs entry into the high-output 12-volt watermaker market. It is the latest in a long line of machines that dates back to the PowerSurvivor 35, the first practical small 12-volt watermaking system.

The 160E uses a standard 2521 membrane in a proprietary housing. It is a dead-simple modular system, utilizing a Leeson 1/3-hp. motor directly coupled to a proprietary stainless steel high-pressure pump. Flexible high-pressure hose between the pump and the pressure vessel allows a great deal of mounting versatility, including bolting the entire system to a bulkhead. All high-pressure fittings are 316 stainless steel.

At 54 lbs. for the entire system, this is one of the lightest high-output watermakers we tested.

When we say dead-simple, we mean it. Other than the pressure bypass valve and the on-off switch-which you provide-there are no gauges to monitor, no product flow meter, and no means of adjusting system pressure, which is pre-set at the factory and is not intended to be user-adjusted. You would still, of course, install the product sampling valve, cleaning valve, and pre-filter, just as with all other units.

The 160E is a gravity feed system, and can only be installed below the waterline.

Our test machine produced 6.5 gallons of water per hour, drawing 17.3 amps at 13 volts-less than we would expect for a 1/3-hp. system. This yields an energy consumption of 34.6 watts per gallon of water-more efficient than average for the watermakers in our tests.

There are several drawbacks to the PowerSurvivor 160E. First, the system is the noisiest of any we tested, putting out 80 dB at our standard test distance of 1′. Furthermore, the reciprocating drive system of the high-pressure pump produces not a steady noise, but one punctuated by a loud popping sound at one stage of the piston stroke. We would recommend mounting this watermaker in a sound-insulated compartment if possible.

The reciprocating pump also produces pulsing in the systems hoses, which should be well-secured to prevent fatigue over time.

This is one of the more expensive watermakers we tested, with a list price of $4,440. Several discount marine catalogs sell the 160E for as low as $3,800. Options include a repair seal kit ($80), an extended cruise kit ($200), and an extensive preventative maintenance package ($420).

On the plus side, routine service of the system, including replacement of high-pressure pump seals-a requirement every 1,000 hours of operation-is simple and well-documented in the excellent instruction manual.

We also looked at two other units from PUR, the PowerSurvivor 80II modular and the newly-designed PowerSurvivor 40E. The 80II is very similar to the 160E, simply scaled down. We did not test it, but since all the other PUR machines met the manufacturers specifications, we expect this one to do the same. The smaller-diameter membrane of the 80II limits you to membranes from the machines manufacturer. It lists for $3,330, and is routinely discounted to about $2,950-about the same as the higher-output Little Wonder.

The PowerSurvivor 40E is the totally re-designed successor to the PowerSurvivor 35, the original high-output 12-volt watermaker. In our tests, its 1/18-hp. motor drew 4.8 amps, producing about 1.6 gallons per hour, consuming 39 watts per gallon of water. It is very compact, and like all PUR watermakers, easy to service and operate.

At 72 dB, its noise level was the equivalent of the quieter large 12-volt machines.

With its light weight (25 lbs.) and tiny footprint-about 15-1/2″ x 15″ x 6″ high-the 40E would be the most suitable watermaker for a single sailor or a couple cruising on a small or very light boat-a multihull, for example-with limited electrical generating capacities, perhaps just a few solar panels and small batteries.

In an emergency, the motor can be disconnected from the 40E, and it can be operated manually by a handle, just like its Survivor 35 predecessor. Because virtually all the parts of the 40E are proprietary, including the pressure vessel, membrane, and pump, you will only be able to service the units with parts from PUR.

List price of the 40E is $2,220/$1,900 discount, with options analogous to those available for larger PUR machines.

Bottom Line: All three of these smaller watermakers are actually the core business for PUR, and fill specific niches where there is no competition. Although the 160e is an easily serviced watermaker, and is more efficient than average, its high price and noisy operation are drawbacks. If the installation flexibility of the 160E is not essential to you, we think there are other 12-volt watermakers of similar capacity and quality of construction that offer better value.

Caribbean Technology The Caribbean Technology YM-200 DC 12 made by Great Water is the highest-capacity 12-volt watermaker we tested. Its rated output of 10.2 gph at 800 psi significantly exceeds that of most of the watermakers in our test.

In many ways, this modular system mimics both the output and sophistication levels of more mainstream engine-driven or 110-volt systems, including a direct drive high-pressure pump, high and low pressure automatic shutoff, and a sophisticated remote operating panel including power switch, pressure regulator, and gauges for system pressure, product water flow, and brine flow.

Power is provided by a 1/2-hp. continuous-duty motor directly coupled to a stainless steel Wanner Hydracell industrial pump. An instruction manual for the pump leads you through the periodic maintenance required. A new oil venting system in the pump claims to have eliminated an earlier tendency of Wanner pumps to weep oil.

A Codeline pressure vessel holds a standard 2521 membrane. Because this is a modular system, high-pressure plumbing includes flexible hose rather than rigid tubing. All fittings are 316 stainless steel.

A Flojet boost pump is standard, allowing the system to be mounted above the waterline. This pump-actually designed as a shower drain pump-adds 3.6 amps to the current draw of the system.

A product flow rate of 10.2 gph is pretty much the absolute capacity of a 2521 membrane, and our test system had no trouble achieving that rate of flow. The downside is that to achieve this flow, the electrical demands of the system are much higher than any other watermaker we tested: 38 amps at 13 volts, or 48.4 watts per gallon.

You would never run this system without running the engine at the same time. The current draw is high enough to drop system voltage down instantly. In all fairness, for maximum efficiency none of the systems drawing 15 amps or more should be operated without running the engine at the same time.

Because of the high current draw, your charging system should be equipped with a big alternator if you choose this watermaker. To take advantage of the big alternators capacity, youll want a big bank of batteries. The system will probably need a 50-amp circuit breaker separate from the main panel, as many main panels do not have service wiring that is really heavy enough for this type of load.

You will also need heavy wiring between the circuit breaker and the systems electrical relay box. The manufacturer recommends 4-gauge wiring, which is heavy and may in some cases be difficult to run.

Obviously, a great deal of planning and thought is required before installing a system of this capacity and with these electrical requirements.

On the plus side, the fully modular design allows the system to be mounted in a surprisingly small space, essentially little more space than is required by a modular 6-gph system.

Weight of the YM-200 is 83 lbs.

The manual includes excellent system schematics, and reasonably thorough instructions for installation, operation, and maintenance of the watermaker.

As you might expect, the size of the pumps and motors result in a fairly noisy system: 80 dB at a distance of 1′ from the high-pressure pump-the big noisemaker in any system. Due to its weight, electrical needs, and noise, the best location for this watermaker is a sound-insulated engine room or compartment, as close as possible to the ships electrical supply.

Bottom Line: The best application for this system is a larger boat with existing electrical capacity, and lacks a genset or a means of installing an engine-driven watermaker.

With a list price of $3,500-which is sometimes discounted through dealers-this is not an expensive system. In fact, on a dollar cost per gallon of water produced per hour basis, this is the cheapest system of the entire lot to purchase. It is not an electrically efficient system, but if the maximum output in the minimum time is your primary criterion in a 12-volt watermaker, the Caribbean Technology is definitely worth considering.

Spectra 180 The Spectra 180, and a few variations on its basic version, are the only watermakers produced by Edinger Marine Services. It is radically different from other 12-volt watermakers, extracting a lot of freshwater with astonishingly low power consumption.

When you first see the Spectra 180, your first impression is that one component-a big DC motor to power the high-pressure pump-has been left out. In fact, the entire system is powered by a small 12-volt pump and motor-about 1/8-hp.-no larger than the water pressure pump on a 35-footer. This is possible due to the unique design of the Clark pump, a remarkably energy-efficient pump created specifically to power this watermaker.

The Clark pump is totally unlike any other high-pressure pump used in watermakers. To oversimplify, the Clark uses two opposing pistons and cylinders with a single connecting rod. System pressure is created by the connecting rod driving the piston into the opposite cylinder. Without a detailed technical explanation of exactly how any why this works, it is fair to say that compared to other methods of creating adequate pressure for reverse osmosis, this is a remarkably energy-efficient system.

The Spectra 180 is also different from other watermakers in that it uses a standard full-size membrane whose pressure vessel is just over 44″ long-almost twice the length of the pressure vessel containing the 2521 membrane used by all the other high-capacity systems in out tests. Mounting this much longer pressure vessel may present problems in some boats. The Clark Pump housing itself is almost as long as the pressure vessel for a 2521 membrane.

According to the manufacturer, they have torn down Clark pumps after 3,000 hours of operation and found no significant wear. In any case, the pump is easy to overhaul in the field by a reasonably proficient owner. An overhaul manual for the pump is part of the system documentation, which is basic but adequate.

This is a modular system, with a remote control panel that can allow basic operation without direct access to the other system components. Total weight is about 51 lbs.

Our test system was a factory demonstrator, configured as a self-contained frame system with some performance compromises compared to the correct, conventional modular installation. Instead of a single large membrane, our test system utilized two 2521 membranes, similar in flux area to the larger membrane.

From a pure electrical efficiency perspective, the Spectra 180 was the most impressive watermaker we tested. With a current draw of 8.6 amps at 13 volts, our test unit pumped out fresh water at the rate of almost 9.5 gph–almost as much as the Great Water system, which draws almost five times as much power. Thats only 11.8 watts per gallon, by light years the most electrically efficient machine in our test.

In addition, at a noise level of 65 dB, this was the quietest system.

The Spectra 180 is not perfect, however. The system runs at low pressure compared to other systems-just 600 psi with our 70F water temperature-and the product water, although perfectly acceptable, had the highest total dissolved solids in our tests. Since product water quality can vary with different membranes, we are reluctant to attach much significance to this slightly lower water quality, which was still well within standards for drinking water.

We have some concerns about the relatively low feed water flow rate through the big membrane. The more water that passes over a membrane, the better it likes it, according to most manufacturers. The Spectras flow rate of about 90 gph is quite small for the large membrane, and we do not know how the longevity of the membrane might be impacted by this.

The ends of the main block of our systems Clark pump were machined from bronze, and showed some signs of surface oxidation at the interface to the Delrin main block. According to the manufacturer, future editions of the Spectra will have stainless steel components in place of bronze.

Likewise, the pressure relief needle valve on our test system dribbled when it was barely cracked open. We were told that this component has also been re-designed.

Our test system utilized brass high-pressure fittings, rather than the type 316 stainless used by every other manufacturer. Some manufacturers claim that the only reason to use brass is to save money, while others admitted to us, a bit reluctantly, that they had never seen a brass high-pressure fitting with significant corrosion, and stainless was generally used for appearance and galvanic compatibility as much as for longevity purposes.

Given the cost of the Spectra 180, we think you should get type 316 stainless fittings, and type 316 pump block components. The price of the Spectra 180 is $4,650, the highest of any machine we tested. You pay a significant premium for a major increase in electrical efficiency. Service, parts, and options prices are similar to those of other manufacturers: $350 for a long-term offshore service kit, for example. The price of the installation kit-$275-strikes us as a bit high for such parts as the three-way servicing and diverting valves that some other manufacturers include in the price of the basic system.

According to the manufacturer, although the system is fully functional and in production, they are still looking at further developments, including a composite Clark pump that would have no metal components. Relatively few of these machines are in use in the field at this time, as the product is quite new to the market.

Bottom Line: The most attractive feature of this system is its energy efficiency. We are less impressed by its price, and by the fact that it would appear to be a system with some room for refinement. However, if being able to run a watermaker without running the engine at the same time is important to you, and if price is less important than electrical efficiency, the Spectra 180 would be the choice among the systems we tested.

Conclusions/Recommendations Because virtually every cruising boat has different needs, priorities, and installation requirements, no single high-capacity 12-volt watermaker is going to fit the bill for every sailor. These are all well-designed, fully functional machines. Each has specific advantages and disadvantages, which we have described.

All meet their manufacturers performance specifications in terms of electrical consumption and product water output. Variances of +/- 10% to 15% from the manufacturers specifications for performance are normal.

The variations in product water quality we found are not significant. All the watermakers produce water that meets international standards for potability. The quality of the water will vary over time with any watermaker and with any membrane. A simple hand salinity tester-available from most watermaker manufacturers-is all that is required for routine checking of water quality. Most owners who use their watermakers daily don’t even bother testing salinity. They start the machine, let it run for a few minutes, taste the water, and if it tastes good, divert it to the tank.

All watermakers have similar maintenance requirements, and all we tested are reasonably easy to service. Your choice of a specific system will be largely the result of specific requirements for your boat and your cruising. The key questions are the amount and shape of space you have for the watermaker, the existing or planned electrical generating and battery storage capacity of your boat, and the amount of water you must make in a specific time frame.

All watermakers are maintenance-intensive. To a large extent, the long-term, hassle-free operation of a watermaker is a function of where and how it is used, and how religiously routine maintenance is performed. None of these machines will stand abuse.

A freshwater flushing system is an important component of a watermaker installation. Of the machines tested, only Village Marine and SK Engineering offer a ready-made freshwater back flush system as an option. While it is an easy system to design and build for anyone capable of installing a watermaker, it should be offered and recommended as an option by other manufacturers as well.

None of these systems is beyond the installation capabilities of a reasonably handy boat owner. If space permits, a totally self-contained system such as Village Marines Little Wonder will be slightly easier to install, but the total difference in installation time between self-contained and modular systems should not be more than a few hours unless there are vexing component mounting problems to solve. Plumbing and wiring connections are essentially the same for modular and self-contained systems, although a modular system with a remote panel will certainly take the longest time to install because of the number of individual components that must be placed.

All installations require attention to detail, particularly when it comes to wiring. We would not recommend you install a watermaker as the first major project you undertake on your boat, since it will require putting in a through-hull, installing heavy-duty wiring, and completing some plumbing that may in some boats be more difficult than it may first appear.

While all watermakers are covered by manufacturers warranties, all specifically exclude damage due to abuse in operation, poor maintenance, or improper installation.

A watermaker is not a use-it-and-forget-it product. Its for those who live aboard. If you don’t use it regularly and maintain it properly, you are wasting your money, and you shouldnt own one. On the other hand, if you are willing to accept the responsibility of maintaining a fairly demanding piece of equipment, a 12-volt watermaker can give you-particularly if you are a cruising sailor who desires long-term independence from shore-a degree of freedom you may not otherwise find.

Contacts- Edinger Marine Service, Inc., 298 Harbor Dr., Sausalito, CA 94965; 415/332-3780, fax 415/332-8527. Great Water, Inc., 5148 Peach St. Erie, PA 16509; 814/838-0786, fax 814/838-8700. Ocean Link, 52 Maritime Dr., Portsmouth, RI 02871; 401/683-4434. PUR, Recovery Engineering, 9300 75th Ave. North, Minneapolis, MN 55428; 800/845-7873, fax 312/315-5505. SK Engineering, 4256 N. US 1, Suite 1, Ft. Pierce, FL 34946; 800/489-0852, fax 561/489-0808. Village Marine Tec., 2000 West 135th St., Gardena, CA 90249; 800/421-4503, fax 310/538-3048.

RELATED ARTICLES MORE FROM AUTHOR

Excellent article, thank you for the research and detailed info.

Agree! Thank YOU

I really appreciated reading your recommendation, especially power consumption from one manufacturer to the other.

I am some how confused with Spectra manufacturing and Katadyn. I thought it was all Katadyn for some time now. When was this test done?.

Great review, except it would have been helpful to have specific TDS figures for the output in each case.

The contact information for SK engineering is wrong. Went to some health insurance company that sounded like a scam.

LEAVE A REPLY Cancel reply

Log in to leave a comment

Latest Videos

How To Make Starlink Better On Your Boat | Interview

Catalina 380: What You Should Know | Boat Review

• Privacy Policy
• Do Not Sell My Personal Information
• Online Account Activation
• Privacy Manager

Yachting Monthly

• Digital edition

Everything you need to know about watermakers

• February 24, 2023

An onboard watermaker will free you from ever worrying again about where your next freshwater stop will be. Andy Pag looks at the latest models available for your yacht

The feeling of autonomy that a watermaker gives a yacht is unique. It transforms that weekend-only cruiser into a go-anywhere, life-on-the-hook, adventure craft, breaking the tether to marinas.

Filling your water tanks at the fuel jetty will always be a cheaper alternative to the eye-watering cost of buying and installing a watermaker, but there will be times when your plans are limited by having no access to a tap or if the only source available doesn’t look particularly appetising. And in the event of a burst pipe or accidentally draining your tank mid-passage, it means you’ll be able to keep sailing at the flick of a switch, rather than having to reroute to refill.

Watermaker desalination process

Watermakers – technically known as desalination units – use a process called reverse osmosis (RO) to make drinking water. By forcing salty water at a high pressure against one side of an RO membrane, fresh water will slowly seep through, leaving the salt and bacteria behind. The output is notably devoid of minerals, but the taste can be a little strange at first. Think of the membrane as a filter so fine that even bacteria and salt molecules can’t get through it.

But as well as the pressure, a membrane also needs to have the water flowing over it to flush away all the stuff that didn’t pass through as it would otherwise block the membrane’s pores. In this way it’s different to a filter because a membrane has a salty inlet, a freshwater output, and a saltier discharge outlet.

Much of the cooking done onboard needs fresh water. Photo: Tor Johnson

High pressure pumps

Creating high-pressure water, which is also flowing at speed, takes a lot of energy, and there are two methods watermakers use to achieve this. One is simple: a high-pressure pump. This can draw a lot of current but it creates the speed of flow needed, and the forceful pressure too. The saltwater is directed to the membranes and the pressure is created by closing down a tap, called a needle valve, at the discharge to build up pressure on the membrane while still allowing water to flow out through the needle valve at the required speed.

High-pressure pump watermakers are fast, but they aren’t the most energy- efficient way of creating clean water. They are usually tuned to produce 60 litres per hour or more but can draw upwards of 500W and while there are 12V versions, they typically use mains voltage pumps and are better suited to being run from a generator than a battery bank.

They’re designed to fill your tanks quickly so you don’t have to run the generator for long. Mechanically, they’re simple, and apart from the high-pressure pump there are no moving parts to go wrong.

A watermaker and its many parts.

Energy recovery

The alternative method is a Clark pump watermaker, also known as an energy recovery device (ERD). This uses a fast-running but much lower-pressure pump which needs less power. To obtain the high pressure required, the pressure in the discharge water is harnessed by a couple of reciprocating pistons and used to boost the inlet pressure. It takes a few minutes to build up pressure and during that time the output is slow and not very clean.

Watermaker running costs

An ERD unit will typically produce 20-60 litres per hour. The lower demand on the pump means it can be reasonably powered by 12V with as little as 9A, and can produce a litre of water with just 4-5Wh of energy. High-pressure units need between two and three times that energy per litre. If you run your boat from solar panels or don’t have a generator, this is the type of watermaker to go for.

Devoid of minerals, the taste can be a little strange at first

In fact, your boat’s power source is the first thing to look at when considering which type of watermaker to get. But it’s also worth remembering that the extra complexity of ERD units make them expensive to buy and more prone to breakdowns.

When choosing an ERD watermaker it’s therefore really important to consider the availability and costs of spare parts because sooner or later they will need servicing.

Most manufacturers have a dealer network that can provide advice, but don’t count on them stocking parts or offering servicing. These machines are notoriously fiddly to repair, and one dealer told me discreetly it’s not financially viable for him to offer a repair service as the time it takes can spiral into hours. That leaves you with the option to send the machine back to the manufacturer at great expense, or do it yourself.

Article continues below…

How it works: The diesel engine: The 4-stroke cycle

Understanding how your diesel engine works is key to knowing how to look after it, and fix it when it…

How it works: Looking after fuel: diesel, hoses and filters

Looking after fuel is essential for keeping your engine running smoothly. Callum Smedley shares his top tips

After-sales service

Spectra has one of the best reputations for after-sales service. In most places you’re more likely to find Spectra and Schenker dealers, but that doesn’t guarantee they’ll have parts in stock, and all manufacturers will ship parts to you. Spectra also offers rebuild kits which come with step-by-step instructions and special tools to get to those hard-to-reach O-rings. They feel like a lot of money for a bag of O-rings, but are a cheaper option than sending the unit back to the factory.

If you’re buying new, a warranty is highly valuable but once it runs out you’ll find out how pricey the parts really are. Some manufacturers give longer warranties if a certified technician installs the system.

Most ERD units are made out of engineering plastics such as Delrin which can split around fittings if over-tightened or if warm water is used during cleaning.

One leading UK dealer who sells all brands told me that since Spectra changed the type of plastic used a few years ago he’s had no returns, unlike rival brands. Spectra were tight-lipped on the material they use when Yachting Monthly asked them for details.

An average-sized watermaker will easily squeeze into the space under a bunk

Watermaker instillation tips

A bad installation can render a good machine useless, so there are a few key points to know. Use dedicated through-hulls for the saltwater intake and brine discharge. Make sure the intake is low enough that it won’t be exposed when heeling or in big waves to prevent air bubbles entering the system. Don’t install the intake where there will be turbulent flow, behind the keel, for example, or near the props and rudders. The discharge should be above the waterline.

To give the pump the best chance of producing the pressure needed, install it as low as possible in the boat. Follow the manufacturer’s recommendations on hose diameters and avoid long hose runs and tight turns that restrict flow.

Finally, use correctly sized wiring as the 12V pumps will underperform if there are voltage losses in the wiring.

Monitoring quality

A Total Dissolved Solids (TDS) meter measuring impurities in the output water coupled to a diverter valve can automatically protect the purity of your tank. Anything under 500ppm is fine to drink but a well-installed system should deliver 200-300ppm.

You can buy inline TDS meters, or stick meters that you dunk into a sample cup to monitor it manually. You’ll see it slipping over time if there’s a problem developing with the pump or membrane.

It’s important to flush or ‘pickle’ your watermaker if you decide to not use it for any period of time

Membrane care

The membranes will produce more output and cleaner output in warmer and less salty seas. For the best lifespan, use them every few days. Drying them out, or running chlorinated water through them will do irreparable damage.

According to Dupont, which makes the widely used Filmtec membranes, they should not be left unused for more than 24 hours, but in practice they can be left for around five days before organic growth risks building up on the membrane, which blocks it and reduces performance. This can sometimes be remedied with an alkaline flush if caught early.

The other thing that can block them is carbonate deposits. In this case, an acid flush will restore some of the membrane’s performance.

If idle for a few days, it’s worth flushing the membrane with fresh water. Some manufacturers recommend doing this after every use, but that’s to protect other components in their systems.

If the machine is going to go unused during the off-season, the membrane can be pickled in propylene glycol. Most manufacturers offer branded pickling solutions and restorative solutions which conform to their warranty and don’t react with other materials in the system.

Avoid using the watermaker in anchorages where other boats aren’t using holding tanks. Although the membrane will sift out e.coli, the pre-filters will become a nasty Petri dish of bacteria.

Pickling tablets will be less aggressive on internal metal components

Don’t leave me this way

Different manufacturers have different recommendations, but, as a general guide, here’s what to do if leaving your watermaker unused for any period of time.

1-5 days: In practice, leaving the membrane sitting in saltwater won’t do too much harm, even though the membrane manufacturer warns against more than 24 hours. Check your watermaker manufacturer’s recommendation though. For instance, Spectras suffer from dramatic internal electrolysis if left soaking in sea water.

1-2 weeks: Definitely flush it through with fresh unchlorinated water. Use a carbon filter to remove chlorine if you are flushing with tap water.

More than a month: Pickle it.

They used to recommend using acid (hence the term pickling) but now manufacturers recommend propylene glycol, which is less aggressive on O-rings and other metal components. Buying the branded solution for your machine will give you peace of mind.

If your boat lives in relatively clean water, think about setting a timer so the machine runs automatically every few days for 10-15 minutes. That’s long enough to flush the membrane and prevent organic build-up.

Enjoyed reading this?

A subscription to Yachting Monthly magazine costs around 40% less than the cover price .

Print and digital editions are available through Magazines Direct – where you can also find the latest deals .

YM is packed with information to help you get the most from your time on the water.

• Take your seamanship to the next level with tips, advice and skills from our experts
• Impartial in-depth reviews of the latest yachts and equipment
• Cruising guides to help you reach those dream destinations

Follow us on Facebook , Twitter and Instagram.