Water, water, everywhere
Article of the Month April 2008Is a watermaker the right choice for your boat?
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Potable water is to a sailor as energy is to a long-distance runner: it must be conserved and parceled out to last. One of the first things guests aboard a sailing vessel learn is that they can’t leave the water running like most do in their homes. I distinctly recall having a visitor aboard Liberty who must not have been paying attention during the “water conservation briefing.” I stood outside the closed head door listening to the constant tinkle of water from the faucet and gritting my teeth as our guest brushed hers. When she emerged, we had a little talk.
Many production boats today typically carry about a hundred gallons of water. We’re fortunate that our Morgan 46 holds three times that. During our first season of cruising the Bahamas, Ty and I decided to see how many days we could go until we ran out of fresh water. Since our tanks don’t have gauges, this was more than mere curiosity. We didn’t want to run out once we left the Abacos, where potable water was more readily available than in the more remote Exumas.
It should come as no surprise that Murphy’s Law operates at sea just as it does ashore. We were into our eighteenth day of the experiment, anchored in Marsh Harbor. The nearest boat was far enough away that Ty and I decided to shower in the cockpit. The warm sun felt great on our skin as we lathered our bodies with soap. This, naturally, is the very moment that the tanks ran dry, telling us that we can go exactly seventeen and a half days before running out of water.
If you do the math, you’ll discover that we use between 17 and 18 gallons per day between the two of us. This seems rather high, but it’s nothing compared to the average household use. It wouldn’t be correct to break that figure down further by stating that we use nine gallons per person, since my husband uses his share of water and then some while showering. To be fair, Ty doesn’t let the water run as long as he does at home, but he doesn’t follow the more conservative wet down, soap up, rinse off routine either. The first time I complained about this, he gave me a steely gaze and said, “I took Navy showers for 14 of my 26 years in the Navy, Suzanne. I am not going to take them on my own boat.”
Roger that, Captain.
A reverse osmosis desalinator can solve the problem for any sailor who doesn’t want to worry about running out of precious H2O. Osmosis is the movement of water from an area of low solute concentration to an area of high solute concentration (thank you, Wikipedia). Those with fiberglass boats know osmosis as a bad thing, where water works its way through the gelcoat into fiberglass laminate, resulting in blisters. Reverse osmosis does exactly what it says: it takes the scientific process of osmosis and turns it around to produce something good… namely, fresh water.
Watermakers pump seawater at high pressure through a permeable membrane that blocks the passage of salt particles. It takes about 10 gallons of sea water to produce one gallon of fresh water. Luckily, there’s no shortage of salt water once you’re at sea. You don’t want to use your watermaker in port. That permeable membrane may block the salt, but it won’t block all the other nasty things found floating in most harbors today.
To install a watermaker or not… that is the question most sailors face when fitting out their boats for blue water sailing. What seems like a simple yes or no decision depends on the following careful considerations:
1. Can we afford it? Other than the hand-held watermakers designed for life raft use, most require an investment of several thousand dollars, even if you do the installation yourself. For cruisers on a budget, a watermaker may be too much of a luxury.
2. Do we have the space for it? Many of today’s modular designs break the system down into components, allowing it to be installed in separate spaces throughout the boat. Our motor/drive/pump (one part) and membrane housing (a second part) take up half of a large locker under our settee. The prefilter assembly (the third part) fits snugly against a bulkhead inside our forward hanging locker. We’re blessed with plenty of storage on Liberty, but many cruisers might hesitate to give up an entire locker for an optional piece of gear.
3. Do we have the power for it? If you’re worried about power consumption, you might opt for the type of watermaker that you tow behind your boat. It’s a nifty concept, but this torpedo-like system may add unwanted drag and requires sailing at about five knots to produce a steady output. Most cruisers choose a 12-volt system. The higher the output in gallons per hour, however, the higher the drain on the batteries. The best time to operate a watermaker in this case is the same time you run the engine/genset to charge the batteries. Before deciding on a particular system, it’s wise to figure out how long you’ll have to run your engine or generator to make up for the added energy consumption. Those using a wind generator or solar power must consider whether their current electrical budget is sufficient.
4. Do we want to put more holes in our boat? Installed watermakers require an uninterrupted supply of clean seawater. The inlet through-hull should be far enough below the water line to avoid pollutants on the surface and to operate at any angle of heel, and be as far as possible from your head’s discharge outlet… for obvious reasons. Ty teed our watermaker’s inlet hose to the existing through-hull for our air conditioner. Since we would never be operating both at the same time, this avoided an extra hole below the waterline. The briny discharge requires its own through-hull, but this can exit overboard from a hole above the waterline.
Watermakers can be expensive, require regular maintenance, take up valuable space, and consume power. All of these factors lead to the final consideration:
5. Do we really need one? Some long-distance voyagers will be the first to brag that they don’t have a watermaker aboard. Certainly, it’s one less thing to worry about in an environment where things break down more often than not. Truly hard-core sailors will tell you that there are more traditional ways to fill one’s tanks than with a modern mechanical gadget. These old salts stop up the scuppers or stretch out tarps to catch the rain when the skies break loose.
Ty and I thought long and hard before we made the decision to invest in our watermaker. We waffled back and forth until a stop in a small island harbor made the final decision quite easy. While tied up at a fuel dock pumping clean diesel aboard, we asked if we could top off our water tanks as well. The price for water, we were told, was twenty cents per gallon. Three hundred gallons at twenty cents would come to sixty dollars. That seemed like a lot to pay just for water, but we reasoned that we could fill our tanks many times over and still not come close to the cost of a watermaker. We had almost decided to skip the big investment of a reverse osmosis desalinator when we asked the dockhand for the source of his water supply.
“From the rain, Mon,” he said.
We nodded and followed his pointing finger. Sure enough, the blue barrels on the pier were filled from gutters running directly from the marina office roof. A row of laughing gulls sat along the roof’s upper edge, laughing, that is, at my expression as I took in the white splotches of bird poop splattered across the shingles.
During our second year as cruisers we took the plunge and installed a watermaker, but we could just as easily have continued as we were. This reflects the statistics of the cruisers who have taken the Seven Seas Cruising Association’s annual gear survey so far this year. Of the 118 respondents, 42%, or almost half, have a watermaker aboard.
The survey didn’t tell if those who went without had made that decision based on finances, space available, power consumption, or simply personal preference. For us, the decision to install one was based on the latter. We no longer have to worry if or when we might run out of water. Ty can take his non-Navy showers, and I can drink all the water I want, knowing that it’s seagull-safe.
Cmdr. Suzanne Giesemann (USN, Ret.) is a veteran sailor and the author of Living a Dream and It’s Your Boat Too: A Woman’s Guide to Greater Enjoyment on the Water. Visit the Giesemanns’ website at www.libertysails.com.
