The laws of physics are working against you. The formula for required
pump horsepower is GPM*PSI/1460. a single 21" membrane needs a minimum
of 1 GPM at 800 PSI which means you need about 1/2 HP. That is close to
40 amps at 12V. You would need a 100 amp alternator to charge the
battery bank and make water at the same time.

I would look at the Waterlog tow behind watermaker if I were you. About
980 Euros. Not as convenient as a traditional watermaker but you can't
build one for that price, it can put out about 20 to 28 gallons in a
full day of towing and it uses no electrical power.
http://www.yach****ermaker.com/

Regardless of Jax's claim that they are fictitious, I have seen a couple
and talked to their owners. One, an Englishman doing an Atlantic
circumnavigation towed his from the Azores to St. Martin and had enough
water extra to wash down his deck every few days.

Paolo Zini wrote:
I have a couple of pages about the one I built on my site under the
"Systems" section. http://www.rutuonline.com/html/watermaker.html


When I made my search, you can believe it or not, but the first place where
I searched is your page....
I definitively need new lenses... :-(

I have initially discarded the watermaker idea, because the cost, but a
do-it-youself version is appealing for a "bricoleur"... :-)

I am building a small cat (cat 254 from Fisher's plans) and i need a smaller
installation.
My main concern is the power source. The cat will have only one small
auxiliary outboard...
The possible alternatives ha
-electric.who refill the batteries? OK is a stupid question, I have the
problem anyway :-)
-small gas engine... I don't like the idea...
-odd power sources wind power generator, propeller generator...
-??
Any suggestion?

Tank you

Paolo



--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com