Go aboard a new Takeuaway 38 at the boat show, and the sales representative will be quick to call your attention to the separate shower enclosure in the head.
What she or he won’t mention is the boat’s water capacity. Even with a shower stall big enough to echo you won’t be able to duplicate shoreside bathing habits. The problem is the size of the tanks, not the size of the head. A 38-footer will have tankage for perhaps 100 gallons of water. A five-minute shower takes 15 to 20 gallons. You do the math.
Even a 45-footer is unlikely to carry much over 200 gallons.
The solution to this inconvenience would seem to be a reverse osmosis watermaker. With a watermaker aboard, sized to match anticipated consumption, your supply of fresh water is essentially perpetual. Not surprisingly, a significant number of the 100 boats we waited out hurricane season with this year were equipped with watermakers. Yet for a period of more than five months, not one boat produced a single gallon of RO water. The reason for this apparent incongruity can be obscure from the armchair, but it quickly becomes obvious once you go cruising.
In many of the harbors where you are likely to anchor, the water is simply too dirty to allow you to run your watermaker. So all boats in the harbor—with or without a watermaker aboard—jerry-jugged water from shore. Adding insult to injury, those boats that had reduced tank capacity in conjunction with installing a watermaker found themselves hauling water more often.
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"The obvious advantage of a watermaker is that it can make you completely independent of local water supplies." |
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The obvious advantage of a watermaker is that it can make you completely independent of local water supplies, and if the watermaker has high enough capacity, it can allow as many lingering showers aboard as you please regardless of weather. That is, provided you can operate it.
Because the expensive membrane is easily damaged by oil or sediment in the water, you will find few commercial harbors with water clean enough to allow the safe operation of an RO watermaker.
If you plan to visit the population centers of the islands and countries on your cruising itinerary, expect your watermaker to be often out of service.
Even where the water is travel-poster clear and you can make freshwater, a watermaker still might not be the best way to fill your water tanks. The economics of making freshwater on a small scale are often overlooked due to the perceived convenience, but cruisers on a budget would be wise to be not so cavalier.
Consider that a small watermaker capable of producing just three gallons per hour (adequate for drinking water but not for lingering freshwater showers) costs about $3,000.
A three gph watermaker draws around eight Ah, so making just 10 gallons per day will draw 26 Ah.
Battery inefficiencies mean you have to put back around 30 Ah. Given the realities of charge acceptance, that is 20 to 30 minutes of engine time every day just to make water.
Expect a 25 to 50 horsepower diesel engine running half-hour per day for a year to consume 120 or more gallons of fuel, adding at least $300 dollars annually to the cost of the water.
Should you plan to handle this electrical demand with alternative energy, you will need a wind generator or solar panels. If you already have a big-blade wind generator, it might appear to have sufficient excess capacity, but unless you are fond of windy anchorages, you are likely to have a shortfall. As for solar power, few boats have excess capacity, so if you need an additional 30 Ah of charging capacity, you will be faced with buying and installing an additional 100 watts of solar cells. In both cases, the cost is $800 or more.
So what is the per gallon cost of water over a one-year cruise? If you make 10 gallons per day for 365 days, that is 3,650 gallons in a year. Spend $3,000 on a watermaker and an additional $800 on a wind generator or solar panels, and the water you make has cost you more than $1 per gallon. The cost is about the same without the alternative energy costs if you factor in wear on your diesel engine. Even after two years, the per-gallon cost drops only to around $0.70 per gallon when you include the cost of required servicing of the watermaker.
A dollar per gallon makes a 20-gallon shower cost $20, but with a three-gph watermaker and two people aboard, this level of individual consumption necessitates four times the alternative power, adding to the initial cost, or two and a half hours of daily engine time, putting nearly 1,000 hours of wear on your auxiliary annually.
A better alternative is likely to be an engine-driven or generator-driven watermaker with a higher gallons-per-hour capacity. Bigger desalinators have a lower per-gallon cost to operate, but only if you can make use of their extra capacity. If, for example, you run a $6,000, 12.5-gallon-per-hour unit all the time, making 300 gallons a day with it, the one-year cost, including fuel cost (but not engine wear), is almost $15,000 or about 13.5 cents a gallon. If you use the same system to make just 20 gallons a day—while you run the refrigeration system—the out-of-pocket cost is only the price of the unit (plus maintenance) but the per-gallon cost balloons to $0.82 a gallon.
The bottom line on watermakers is the bottom line. They are expensive to buy, not always trouble free, and they require long engine hours to produce significant volume. And they have no use when you return home—where all the water you want is free at your dock.
What are your alternatives? In many parts of the world, and particularly in the tropics, enough rain will regularly fall
on your boat to more than meet all your freshwater needs. A half inch of rainfall drops more around 100 gallons of water on the deck of a 38-foot boat. All you have to do is catch it and get it into your tanks. This can be as simple as plugging the scuppers and opening the on-deck fill cap to let the water run into the tank rather than over the side. Since we walk, land fish, and occasionally clean conch on the deck, Olga and I have never been comfortable with this method aboard our boat, but many cruisers prefer it to all other catchment schemes. Let the rain rinse away salt deposits and other contaminants for a few minutes before you plug the scuppers.
A compromise is to “fence” the cabin top with low molding to catch the rain and direct it into a hose leading to the tank. The cabin top sees less traffic than the rest of the deck and is less likely to contaminate the runoff.
We prefer to let the harbor awning do double duty as a rain catchment. This requires a well rigged awning because rainstorms are often accompanied by wind. A harbor awning that you have to take off every time the wind pipes up is a nuisance anyway, so once you have a good awning design for your boat, using it to catch water requires nothing more than installing drains of some sort in the low spot(s) of the awning. Some designs incorporate a canvas gutter along the outboard edges. During an average month in the relatively dry Bahamas, a 15 by 10 awning can funnel close to 500 gallons of sweet water into your tanks.
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"Perhaps the easiest way of stretching your water supply is to use only the amount needed. " |
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Perhaps the easiest way of stretching your water supply is to use only the amount needed. Limit pressure water to the shower only, installing foot pumps at all basins to allow precise water delivery. For showering, use only a handheld shower head with a finger-tip shutoff so all the water strikes your body and you can stop the flow instantly. (A sprayer with a spring-loaded shutoff intended for a kitchen sink makes an excellent boat shower head.)
Never let the water run while you lather.
We carry shower conservation one step further, using a pump garden sprayer for showering. The spray head delivers a fine mist that provides an efficient shower using an amazingly small amount of water, typically less than half a gallon. If you are skeptical, consider how you clean windows and counters, not by flooding them but by spritzing and toweling them off. You can clean skin the same way just as effectively. Try it before you snub it. At the very least you will use the sprayer to give yourself a miserly, salt-removing freshwater rinse after swimming.
Reduce freshwater consumption by substituting seawater at every opportunity. Install a seawater spigot in the galley before you go cruising. If the water outside is clean enough to swim in, it is clean enough for all dishwashing.
It might also be clean enough for cooking. Boil eggs or steam vegetables with it. A cup of seawater has approximately two teaspoons of salt in it, so instead of adding the called-for tablespoon of salt when boiling pasta, for example, substitute a cup and a half of clean seawater, conserving an equivalent amount of fresh water. It adds up.
A third water-management strategy is adding extra water tanks. Tanks do reduce the available stowage space for other items, and they add substantial weight when full, but greater water-stowage capacity allows you to better take advantage of any water source, whether from shore or sky. Water in your tanks is a bird in the hand while the ability to make water can turn out to be no better than two birds in the bush.
Watermakers make a lot of sense for cruisers going where water is difficult to obtain. For the rest of us, a watermaker can deliver less convenience than you might expect at a cost higher than the alternatives. Be cautious.
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