Do you need a watermaker on your boat?

While most boaters don’t need a watermaker, clean H20 will allow you to kiss the dock goodbye in pursuit of adventure.

UPDATED:APR 29, 2021ORIGINAL:OCT 8, 2018

Mike Smith, powerandmotoryacht.com

Is It Time For a Watermaker?

Watermakers keep passage making folks hydrated, but what about the rest of us? Here are a few reasons to love a watermaker.

Watermakers get a lot of ink in boating magazines, including this one. But lots of boaters don’t really need a watermaker, or the hassle of maintaining one, because there’s clean drinking water as close as the dockside fresh water spigot. So why do we write about these things, and why do you, our readers, keep reading about them? Because watermakers say cruising and tropics and living off the grid, things that the majority of boaters, this writer included, dream about doing someday. Undeniably, however, there is a minority of boaters out there for whom watermakers make a lot of sense—the folks who visit the Bahamas periodically, for example. Or the shores of Old Mexico.

Not so long ago, in the days before the advent of small, affordable watermakers, offshore voyagers aboard small or mid-size boats didn’t have a choice. They started with a limited number of gallons of fresh water, used mostly for drinking and cooking, and made it last until reaching port. For a sailboat, that could mean weeks, but even for powerboats, crossing oceans is a slow process, so fresh water was treated as a precious commodity. (Displacement-hulled power cruisers are most efficient at a speed roughly equal to the square root of their waterline length; a 36-foot LWL passagemaker cruises most efficiently at about 6 knots, for example, or 13 days from Bermuda to the Azores, if all goes well.)

Watermaker maintenance chores include regular oil changes, filter replacements and salinity probe checks. Photo courtesy of Saunders Yachtworks

But that was then. Today, few people would set out to cross an ocean without a watermaker, an onboard Gunga Din keeping everybody well-hydrated, and supplying enough clean H₂O for the occasional shower, too. Use it every couple of days to top-up the tanks, clean it now and then, replace filters once in a while, and your watermaker will be an ideal shipmate. So, installing one is a no-brainer for serious cruising folks.

What About You and Me?

There’s a rub when cruising in the tropics, however, or most exotic locales: Dockside fresh water is often terrible tasting, you usually have to pay for it and sometimes whatever crawlies live in it give you a bad case of gastrointestinal distress.

Now, I’ll grant you that paying for water isn’t so bad

; you can buy a lot of it for the price of a watermaker, and a good filter system can help with the taste (read on). But who wants to get sick on board? And who wants to alter course to search for fresh water when the fuel tanks are still half-full? Not me—I’ll take a watermaker every time. But I don’t need one that desalinates the equivalent of the Central Park Reservoir every day either, and I don’t want one that requires 120-volt juice to do it.

Why 12-Volt?

There’s no question that folks who live with the genset running 24/7, and/or who need lots of H₂O, will want a 120-volt, high-output watermaker that can desalinate hundreds of gallons per day. But most folks can get by with a lot less. Since the engine’s running all the time while cruising, the alternator will easily replace the battery drain of a 12-volt watermaker, even a big one that draws 15 or 20 amps while making 15 gph or more.

Sea Recovery’s Ultra Whisper 400 desalinates water at 16.5 gph

Firing up the genset just to power a watermaker uses fuel unnecessarily though, a factor to consider when stretching the boat’s legs to reach a faraway port. In my opinion, a genset isn’t necessary for long-range voyaging—I spent four years cruising on both sides of the Atlantic aboard a 12-volt boat, and never felt deprived—and a watermaker will fit nicely into the space made available by not having a genny.

Also, at anchor in clean water, a 12-volt watermaker can fill the tanks without everyone having to listen to the genset’s roar, the battery drain replenished by solar panels. I’d want high-capacity battery banks for this, but any serious cruising boat will have them, along with an inverter for occasional 120-volt needs. Note I said, “clean water.” Watermakers are designed for desalinating clean ocean water; avoid operating them in dirty, polluted harbors, or where there’s a lot of silt in the water, or anywhere you’d think twice about jumping overboard for a swim. At best you’ll be cleaning the filters often under such circumstances, at worst the membranes will get scuzzy with stuff you don’t want in your water. If possible, desalinate while underway between harbors.

Spectra’s Ventura 150c is an ideal watermaker for small or mid-sized vessels with average needs. The unit can operate in temperatures up to 110 degress—so maybe mounting it in the engine room won’t work for tropical cruising. But the Ventura 150c is modular, and the pieces can be stashed in lockers or under settees, etc. It produces 6 gph, drawing about 9 amps of 12-volt juice in the process. Use it when the engine’s running, and amp draw doesn’t matter, but a healthy battery bank can handle the load, too.

Watermakers should be operated every few days, at least, to keep their innards clean, which often doesn’t happen if you don’t live on the boat. Otherwise you should flush them out and “pickle” them with preservative, another annoying maintenance chore. The Ventura 150c can be controlled remotely from your phone, so you can run your watermaker when you’re not aboard the boat. If you don‘t need yet another thing controlled by your phone, the Ventura 150 (no “c”) is the same watermaker without connectivity.

Sea Recovery manufactures some of the most compact watermakers available, including the Aqua Whisper Mini.

If you don’t like the Spectra, try Sea Recovery’s Aqua Whisper Mini. It comes as both a compact self-contained unit or in modular configuration, and produces 7 gph, but draws 27 amps at 12 volts. Generator-minded skippers can buy the AC model. The Aqua Whisper Mini can operate at ambient temperatures up to 122 degrees. If 7 gph isn’t enough for you, Sea Recovery’s Ultra Whisper 400 desalinates 16.5 gph, and draws only 21 amps at 12 volts. It’s quite a bit bigger than the Mini, though. Horizon Reverse Osmosis, Village Marine and several other companies also build a full line of watermakers (both AC and DC) for large and small yachts. One minute with Google will uncover them.

So here’s the bottom line—there’s a watermaker for almost any boat. Shop around and find one that meets your needs. But watermaker or no, before casting off on a bluewater passage, have enough water on board to get you to your destination with minimal usage. Don’t rely on the watermaker to make up for inadequate freshwater tankage. Use it for more freedom of water use, like requiring crew to shower every couple of days whether they need it or not, while keeping the tanks topped-up. If/when the watermaker packs it in, you want to have sufficient freshwater to get you to the next port, even if everyone’s in need of a wash when you finally arrive.

Filter It

If you want water on board that’s fit to drink, you need filtration, even in the United States. Most domestic drinking water is safe, thanks to EPA regulations requiring the removal of the most dangerous contaminants. But even if the water is technically safe, it can look and taste funky due to other, permissible contaminants.

Moreover, even if the water coming from the dockside tap is fine, fiberglass water tanks can turn it sour, especially if you haven’t cleaned them in a while. When was the last time you cleaned your tanks? I’m guessing never. So step one on the path to pure water is to do it now. Add a cleaner/treatment, like Starbrite’s Aqua Clean, let it slosh around, then pump the tank dry through the galley and head faucets. Refill the tank, adding Starbrite’s Water Conditioner to keep the tank and plumbing sweet.

Clean tanks make the filter’s job easier. The ideal setup for boats with more than one freshwater outlet—that’s just about every boat—is a charcoal filter at the freshwater pump. Boats with dockside pressure-water should have a filter at the inlet, too. In either case a flowmeter will be handy for determining when to change the filter cartridge—a dirty filter is worse than no filter at all. The option is to mount a filter at each faucet providing drinking water, including the icemaker.

Shurflo makes good, reasonably priced filters. If you want to spend more for something fancier, check General Ecology’s NaturePure and Seagull IV systems. Or visit West Marine where you’ll find a selection of filters, from simple in-line models to more complex systems.

If you want the ultimate in clean water, invest in ultraviolet disinfection, working in combination with a standard filter. Filtered water runs through a clear tube where it’s zapped with UV rays that kill microorganisms. The only downside to this setup is that it requires electricity. The Water Fixer and Atlantic Ultraviolet make UV purifiers for both 12- and 120-volt systems.

Finally, Sea Recovery’s UltroClear DF is a super filter—almost a water polisher—that is installed between a watermaker and the ship’s tanks. Its carbon filter “double-purifies” the water, according to Sea Recovery, ensuring that only “ultra pure” H2O enters the boat. The smallest UltroClear DF model can scrub 400 gallons a day. However, finding a place to install it could be a challenge: It lives in a case measuring 28" by 19" by 17.5", so it’s as big as a small watermaker. But I’ll bet the water tastes great.