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Old 16-01-2010, 19:04   #1
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Can a Watermaker Be Used While Underway ?

Hi, First post,
I'm looking at getting a 12v watermaker and want to know if they work while underway.
The big issue for me is that I plan to use a prop shaft alternator to get more power while sailing and would like to use some of those amps to make water if feasable.
Any thoughts on this idea appreciated.
Scott
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Old 16-01-2010, 19:09   #2
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Yes, you can run the watermaker while underway. Make sure that your saltwater intake remains well-submerged because you don't want to suck in any air.
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Old 16-01-2010, 19:11   #3
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Watermakers are sensitive to air bubbles in the raw water. There is a possibility of damaging the membrane/pump with prolonged use in that fashion. The areation can also cause issues with the product quality.

We created a tank with baffles and a breather tube (that vented above the water line to prevent siphoning) that allowed water to flow in and the air to vent out. The raw water was then picked up after baffles that then fed the WM a bubble free supply.
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Old 16-01-2010, 19:17   #4
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Great answers and thank you both for the quick reply.
I like the tank idea to reduce the risk of air in the intake.
Scott
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Old 16-01-2010, 19:26   #5
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No problem.

While transiting when ever we were wasting electrons from solar, wind or motors (batteries fully charged) we always made water. We ran into the issue of bubbles in the raw water flow. Any extra water over the water tanks was dumped into the washing machine. We liked our clean sheets, even when offshore.

Just make sure that when you build your tank that something that will not fail and that the vent is higher than your water line. Otherwise you open a boat to water from the outside, possible flooding.
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Old 16-01-2010, 19:42   #6
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OK, I'm looking at a the powersurviver 80E which produces 3.5 gph so about how large of a tank(pre tank) would you recomend?
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Old 16-01-2010, 20:03   #7
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The tank i used is about 5-6 gallons (PVC pipe with baffles and capped) to feed a 6 gph WM. It wasn't done with any calculation or experimentation it was what was on hand. the idea was to create a baffled container that also held enough raw water to fed the pump.

It was the baffling that actually helps separate the air out.
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Old 16-01-2010, 20:12   #8
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Baffling...
Got it!!
Thanks
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Old 16-01-2010, 20:20   #9
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Don't forget the vent tube. The air has to go somewhere
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Old 16-01-2010, 20:25   #10
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baffles or baffling????
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Old 16-01-2010, 20:29   #11
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Nothing Baffling about Baffles.
And right you are about the venting, I wont forget.
Thanks Much
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Old 16-01-2010, 22:00   #12
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I looked at the Power Survivor but decided it was too hungry on power for the amount of water produced.

I installed a Schenker 35 litres per hour (~9 US Gals per hour) which was a little more expensive but it only draws 8-10 Amps !! It uses a fluid amplifier system that only needs a low pressure pum (bit like Spectra).It has an automatic flushing facility as well, selectable for each time you use it or not... I use it every day when underway...in fact today I had to motor 11 hours, ran the watermaker and after 2 hours water was coming out the vent...so we were full up!

The air bubble story is significant ...they don't like air, but if the salt water inlet is near the center line , it;'s unlikely you'll get air in it when you're moving...wouldn't make sense to run it in a F9 gale though

the Schenker unit has a depressurising valve which allows you to get all the air out simply.
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Old 17-01-2010, 00:26   #13
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Put the intake as low as you can get it , alongside the keel, amidships.
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Old 17-01-2010, 04:46   #14
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Cross contamination

Not exactly the OP's question, but has anyone considered the issue of cross contamination between the WM pick up and the drains on the boat, let's say the sink drain which may contain chemicals damaging to the membrane (chlorox, dishwashing liquid etc).

The only obvious place for the WM pick up on my vessel is pretty close to the sink drain and I figure I'm going to need a small sign reminding the crew not to use the sink whwn the WM is running.

Anyone else considered this or do we expect the dilution to be so great that it wouldn't cause a problem.

Duncan
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Old 17-01-2010, 05:14   #15
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Here's what worked for us. We had a Pur 40E on the previous boat and cruised 2 1/2 years, using the watermaker about 2 of them. We currently have a Pur 80E. We wanted and want to make water in silty conditions so added another pre-filter (Lowe's $30, NOT marine $300 +) with a 5 micron filter in the second one.

After a lot of trial and error found that using our raw water pump (auto cut-off like the fresh pressure water system) and a 2 Gal accumulator feeding the pre-filters to watermaker eliminated all air problems that seemed to be more from cavitation than anything else.

The feed water is teed off the engine raw water intake, which is always under water.

We've made water offshore underway, power and sail, and at anchor. Even in our very silty bayous. Never in an industrial type area where there could be oil on the water. Oil and chlorine will quicly destroy the membrane. Of course the prefilters will load up a lot quicker in dirty water.

Speaking of prefilters, they can be simply cleaned and reused as long as they're in good shape. That is not collapsing. We changed the 20 micron once in the 2 years. We changed the 5's a few times because they're a bit harder to clean. We used the "string" type. Be sure NOT to use a paper filter.

Rick
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