DIY Watermaker

[Tellie]

Originally Posted by Alan Wheeler

Apart from customising an installation to suit your boat, is there a big saving to be made in building yourself?? I thought the cost was mostly the filter/membrane system.
And just how long do you get out of a membrane before it has to be replaced???

Two schools of thought. If you are the type that puts a dollar amount on your "time" then no, a self built unit costs as much as a smaller pre-packaged unit. The real time put into tracking down parts and the learning curve that certainly goes along with it is extensive enough. When I built mine, I thought and still believe now, the apparent savings was worth the time and education gained. But I have time, whereas I know others who work full time and still want to squeeze in some sailing time do not. I spent countless hours at Sailorman, Budget Marine, West Marine, Boat Owners etc., five trips to my local Yanmar guys just to get the PTO pulley right, the Cat pump was easy to order, getting the right 12V dual clutch was three weeks of phone calls and returned parts, pulling the boat for a new thru hull (and the new bottom job while I was at it). I scoured E-Bay for pumps, filter housings, and bought parts I really didn't need like 30 sub standard filters I later learned that though they are 5 and 20 microns aren't worth much for an RO system and on and on. Then comes all the custom fitting work, glassing in mounting areas, custom welded engine pump brackets, etc. Now personally I don't mind the grunt work, but if I was to give my time spent even the minimum wage I could have easily bought a Spectra (cheap plug) that more than met my needs.
But back to your question, a new 40" membrane housing with end caps and gaskets can be had for about $250 and a new SW2540 membrane for about $250 as well. So unless you opt for two 40" membranes as I did the cost of them are about a 1/5 of the cost of the home built WM unit. The $64 question, how long do membranes last? A well taken care of membrane should last 5 to 8 years, perhaps more depending on too many variables to list here. The reality is that most are not well taken care of. To put it simply they are a pain in the arse to maintain properly as many here already know. If I were to build again I'd scrap the Cat pump and look for an E-Bay Sectra pump and build around it. Otherwise an entry level watermaker is not relly such a bad price after all.

[Latitude9.5]

Like Tellie said, after you put the system together yourself you have an very good understanding of how everything works... and hopefully why it doesn't if that's ever the case.

I managed to suck up some crap in the intake in mine while we were in the bahamas, burned up the high pressure pump, so I had to rebuild that, I now know more about the Cat pump then I ever hoped to

We met some friends over there who had an 8 gph electric watermaker and I laughed, but later thought about it and have decided I would prolly rather have the 8gph electric DC over the 40gph engine driven, why? Well when i run mine i have to be tied to the boat, i have to be monitoring things and I'm burning diesel and putting wear on the motor. The 12v even if it ran all day, I could be off snorkeling or even taking a nap while i made water, worst case I'd have to run the generator and charge some batts. Who knows maybe i'd change my mind after playing with the electric one for a while.

[Brent Swain]

Forget electric drive. It is a major source of trouble for watermakers. Go for engine drive. Don't go undersize. It takes too long to make enough to flush them out properly. You have the power with engine drive. The one in my book can be built for a fraction the cost of most electric drive ones and costs under $1,000 for parts, at an output of 540 GPM, so why would you spend more on a smaller one. 540 GPM sound like a lot, but it just means you have to run them for less time or less often.
Just put the belt on every four days and you don't need electric clutches , etc.
I put the pump outside the engine compartment with a removeable panel for the belt to go thru when I want to use it.
Brent

[scotte]

Originally Posted by Louis Riel

The one in my book can be built for a fraction the cost of most electric drive ones and costs under $1,000 for parts, at an output of 540 GPM

Are you certain you have that figure correct? Maybe M=month?

[Latitude9.5]

yea wow, that IS impressive. I could fill my tanks in less than 30 seconds!

[Tellie]

Louis knows from where he speaks, a typo to be sure.
But just think of the possibilities, a watermaker and jet drive all in one.

[Latitude9.5]

I built mine from the Leo Litchfield plans, like i said it's a 40 gph, can be made into an 80 gph pretty easily, but as I stated earlier, there are advantages and disadvantages to both.

[Cheechako]

Aquamarine, Inc - Home I have used these guys for an engine drive unit I built. They are pretty helpful. It takes a pretty big motor to make much water at 12V though. Engine drive is super. Need to motor for an hour? Make 20 gals while you're at it! In the simplest form a water maker is just a high press pump, a membrane, a needle valve, a relief valve for safety and an oil filled psi gauge. The pump creates pressure, the needle valve (after the membrane) dumps water overboard until when closed partially , when the needle valve restricts flow it creates pressure which forces water through the membrane. Close the needle valve until the correct pressure for your membrane is reached. (600 psi???)

[svcattales]

Originally Posted by Latitude9.5

We met some friends over there who had an 8 gph electric watermaker and I laughed, but later thought about it and have decided I would prolly rather have the 8gph electric DC over the 40gph engine driven, why? Well when i run mine i have to be tied to the boat, i have to be monitoring things and I'm burning diesel and putting wear on the motor. The 12v even if it ran all day, I could be off snorkeling or even taking a nap while i made water, worst case I'd have to run the generator and charge some batts. Who knows maybe i'd change my mind after playing with the electric one for a while.

Thanks for the great philosophy. I looked at the 40 gal/hr homebuilt and I didn't want the complication of extra pulleys and belts on the diesel. We used an old PUR 35 for several years (1.3 gal/hr) and we survived just fine. Obviously, we had to conserve and took "sea showers" instead of "Hollywood showers" and caught rain water when available. One of the nice things about 12V is we could run it off our solar panels and although it was slow we could run it without constant supervision. I just ordered the plans for a 12 V homebuilt from Bob Englar on Ebay. His design puts out 6 gal/hr and costs less than $1600 for all the parts. He provides all part numbers and sources for all the components so it looks fairly easy to build. I'm not sure how many amps it draws so I may not be able to run it off the solar panels. With 6 gal/hr we will be in the lap of luxury.

[Latitude9.5]

Originally Posted by svcattales

Thanks for the great philosophy. I looked at the 40 gal/hr homebuilt and I didn't want the complication of extra pulleys and belts on the diesel. We used an old PUR 35 for several years (1.3 gal/hr) and we survived just fine. Obviously, we had to conserve and took "sea showers" instead of "Hollywood showers" and caught rain water when available. One of the nice things about 12V is we could run it off our solar panels and although it was slow we could run it without constant supervision. I just ordered the plans for a 12 V homebuilt from Bob Englar on Ebay. His design puts out 6 gal/hr and costs less than $1600 for all the parts. He provides all part numbers and sources for all the components so it looks fairly easy to build. I'm not sure how many amps it draws so I may not be able to run it off the solar panels. With 6 gal/hr we will be in the lap of luxury.

If you don't mind, keep me posted on the process, at that price I would REALLY be interested in building an electric one myself, I am wondering if he's using one of the recovery electric pumps or something different.

[Strygaldwir]

I largely built a twelve volt system, but, it is based on using a hydraulic entensifier. Basically, after spending several months researching, I was unable to find a twelve volt pump that generated sufficient flow and pressure to push a sw2540 membrane.

The intensifier give you about 7 times the input pressure on the output side.

I got a Spectra/Clark hydraulic entisifier, I connected two agricultural Surflo pumps, Got a high pressure membrane houseing, put on lots of GE house filters from Lowes, lots of valves and for arround $1k have a 200gpd water maker. Uses about 2.5 amps per gallon. I would run it once every day for about 1.5 hours. Worked great for two years. Pickled the membrane, but I don't expect it to be servicable when I put it back into action. Did some rather extensive post back when I was making it. Should be somewhere in the archieves.

[northerncat]

i have tried looking for a spectra intensifier but it doesnt seem that you can buy them seperate anymore, i to would be interested in an up date on those internet plans
sean

[svcattales]

Originally Posted by Latitude9.5

If you don't mind, keep me posted on the process, at that price I would REALLY be interested in building an electric one myself, I am wondering if he's using one of the recovery electric pumps or something different.

I sent an e-mail to Bob about the amp draw on his design. I have 3 different pump motor options which varies water output and amp draw. A 1/2 HP pump will draw 39amps and produce 8.6 GPH; a 1/3 HP will draw 27amps and produce 6.5 GPH; and a 1/4 HP will draw 21amps and produce 4.9 GPH. I will probably opt for the 1/3 HP pump motor since I can run this off my solar panels with some help from the wind generator. I don't know whether this pump uses an intensifying technology like Spectra, but since it takes about 4.2 amps per gallon of water I doubt it. This system isn't as efficient as the production models, but I think purchase cost, simplicity, and maintenance cost still make it a good value for me. There are times when the sun is out strong, the wind is honking, and the batteries are topped up. When that happens I'll be happily drinking a beer while I watch my water tank fill and toasting the other cruisers shlepping water to their boats in 5 gal jugs.

[JusDreaming]

Originally Posted by Alan Wheeler

Apart from customising an installation to suit your boat, is there a big saving to be made in building yourself?? I thought the cost was mostly the filter/membrane system.
And just how long do you get out of a membrane before it has to be replaced???

I used the plans Guy published, and it cost me 2300. for a 20 gallon per hr unit. So the savings were considerable!
By the way Guy, thanks for you dsign article, it works great, I could not have done it without you article

[George Elliott]

There's too many variables to put an hour max limit on membrane life, depends on how kindly you treat them. But if I were to build a 12v 8 gph unit I'd start by copying one of the small units like the Little Wonder. Membranes like to be used, an hours each day is better at suppressing biological growth than 3 hrs every 3 days. I like the Little Wonder style, easy to build and easy to source parts for and for a small boat enough water. I built an engine drive with a 20" membrane all I get out of it is 8 gph, but it works in conjunction with mechanical refrigeration. Next boat would be all dc though. good luck. George