Equipment & Gear used on our CR Yachts 400DS sailboat
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Watermakers, what they do

The modern watermaker is a miraculous machine, taking undrinkable salt water and, with a modest amount of energy, producing a steady supply of pure, fresh water. A well-designed, properly maintained watermaker can add significantly to your safety and comfort while cruising and thousands of experienced voyagers swear by them.

There are lots of reasons to install a watermaker to make your cruising (or racing) more enjoyable:

- Emergency water when your tanks spring a leak and dump 200 gallons of water in your bilge. Water can also become undrinkable if you fill up with crud in some cruising "paradise" and lack the ability to purify it.

- You can reduce your water burden by taking some water in your tanks and supplementing it by using the watermaker. This is obviously of great interest to racers, but can also allow a cruising sail or powerboat to perform more efficiently by cutting down on weight (and, at 8.2 lb. per gallon, it doesn't take much water to push the bootstripe under!)

- You can extend your range if you have been water-capacity limited. Instead of planning your trip based on where you can fill up your tanks, you can push on knowing that you can make your own.

- You can save money in foreign ports, where potable water can be very costly. Many Caribbean ports charge $0.10 per gallon or more to fill up water tanks, which doesn't sound like much until you realize that you've always thought of water as free.

- Finally, you'll be assured of having a safe water supply on board. The water quality in many parts of the world is questionable, and we could all do without a gut-wrenching bout of turista caused by some unattractive parasite.

How they work
Reverse osmosis watermakers, like those from Spectra, PUR and HRO, produce fresh water by pressurizing saltwater to around 800 psi and forcing it through a semi-permeable membrane. The key word here is semi, since the membrane appears to be about as permeable as a fiberglass boat hull. Somehow, miraculously, water molecules can pass through, but practically all contaminants (like salt, bacteria, viruses, grit, etc.) are left behind. The resulting "brine" is discharged overboard, and a new batch of saltwater is introduced. This is a continuous process, with about 10% of the incoming saltwater being turned into fresh water, and 90% being discarded.

Since PUR watermakers were originally designed to be powered by hand, PUR developed an energy-saving method of taking the rejected brine (still at very high pressures) and using it to assist in pressurizing the incoming water. This "energy recovery" principle made it possible for a person to hand-operate a small watermaker and produce enough water to hydrate 25 people in a life raft. The original product, the Survivor 06, eventually led to the production of other manual and electric watermakers which also incorporated the "energy recovery" technique, which greatly reduces energy consumption compared to units which do not use some means of recovering the energy.

How much is enough?
What's a reasonable water budget for voyagers? Starting with a minimal approach, the W.H.O. (World Health Organization) recommends at least a liter of fresh water per day to maintain hydration. Obviously, that figure is for survival conditions, and not how we envision our summer vacation. Donald Street, in The Ocean Sailing Yacht, says that fresh water consumption can be 2 quarts per person, per day, assuming that this is augmented with other liquids and that normal water conservation methods are used (saltwater showers, rinsing veggies in saltwater, etc.) Linda Dashew comments in Offshore Cruising Encyclopedia that her family of four used five gallons of fresh water per day initially, but graduated to 12 gallons per day as their children grew and their water storage capacity increased.

So, shoot, if we are going to have a watermaker on board, we'd probably plan on a luxurious 2 gallons per person per day and really live it up. That translates to approximately 80 minutes of PUR PowerSurvivor 40 operation per person per day, or half that much using the PowerSurvivor 80 II. And that, in turn, translates to about 5Ah per day per person for lots of fresh water.

Based on this crude analysis, most small cruising boats can exist harmoniously with a PowerSurvivor 40, and not have to operate it day and night. When your consumption, whether due to having too many friends, or a profligate use of water, rises to over 10 GPD, we'd go with the PowerSurvivor 80 II. Should your consumption be over 20 GPD, we'd recommend the PowerSurvivor 160.

Saving water aboard
Cruising books are full of recommendations on how to reduce your fresh water consumption while passagemaking. While we'd love to have enough water not to be concerned with conservation, reality must prevail. Here are some tips:

1 Plumb your galley, and possibly your head, with saltwater. One of our customer/advisors recommends that you install a Y-valve on the inlet water to the pressure water pump. When in conservation mode, use the pressure pump to deliver saltwater to the galley and head. Rinse vegetables and clean pots and pans with reckless abandon! The ocean will provide as much water as you require. Use a foot pump for fresh water for drinking, sensitive recipes, and a final rinse of dishes. In non-conservation mode (as when marina-hopping), change back to fresh pressurized water.

2 If no pressure water, have salt and fresh water pumps in the galley. We'll bet that using foot pumps instead of pressure water can save 50-75% of the water consumed on board. And having a dual pump set-up with fresh and saltwater will really stretch the drinking water supply.

3 Cook and clean with salt water. While you can't substitute saltwater for fresh in all applications, it can be used to cook certain types of fish, and can be used with fresh water to boil pasta (10-20% salt). Vegetables can be washed in salt water too.

Watermaker on Mad Dog Voyager