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Used to see articles in Mother Earth News about using "hydraulic Ram Pumps" to pump small amounts of water to a higher point using the momentum of a larger amount of water. Said pumps used no input power other than that produced by the passing water.
So, what do boats have lots of? Water moving up and down (waves). Use this motion to drive a piston to pressurize a smaller amount of water for an RO system to make fresh water.
A similar device is something I have seen advertised, a pump mounted so that the surging motion of a boat attached to a piling pumps the bilge of a boat. Ingenious but practical?
 

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A watermaker needs about 800 psi to push the brine through the membrane. It won't work.
 

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Used to see articles in Mother Earth News about using "hydraulic Ram Pumps" to pump small amounts of water to a higher point using the momentum of a larger amount of water. Said pumps used no input power other than that produced by the passing water.
So, what do boats have lots of? Water moving up and down (waves). Use this motion to drive a piston to pressurize a smaller amount of water for an RO system to make fresh water.
A similar device is something I have seen advertised, a pump mounted so that the surging motion of a boat attached to a piling pumps the bilge of a boat. Ingenious but practical?
Once again, most boats spend most of their time at a dock, on a mooring or at anchor, where it is calmest. I'm not going to choose a rough anchorage a couple of days a week, just to run the watermaker rather than burn a gallon or so of fuel.
 

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A ram pump will put out an intense amount of pressure pulses or pressure spikes ... pulses that are or may be invisible to normal pressure gages, etc.
RO Membranes easily rupture and break with additional 'pulses' and higher than 'sensible' pressure input limits; such membranes require constant flow / constant pressure.

A pulsing pump will be a functional and mechanical disaster for a RO membrane.
 

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Here is a link to a hand held water maker. pumping the handle is all that is required. this could easily be adapted to a motion type of actuation.
How about mounting it to the boat with a handle extended over the dingy which would be bobbing around behind the boat and pumping the handle at the same time.

https://www.readymaderesources.com/...inator-watermaker-free-shipping/prod_629.html

since this water maker uses a pulse action to pump water through a membrane it would seem we have been hearing some erroneous info so far

I used to build Ram pumps. The way they work is this. You lay a piece of pipe along side of a creek or burry it is best so you don't loose hydraulic power caused by the pipe jerking all over the place. lets say the pipe is 100 feet long. water flows into at the top and must have some pretty good fall say 6 foot in distance of 100 feet. the ram pump is connected to the bottom. it has 2 one way valves in it one to stop the flow of water and the other to trap pressurized water for the out put. The water begins to flow through the 100 foot pipe and when it gets enough speed it causes a one way valve to slam closed which in turn creates a hammer effect pushing water through the other one way valve which is trapped as output water. when the second valve closes it causes a small momentary negative pressure which causes the first valve to flop open. starting the cycle over again
 

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since this water maker uses a pulse action to pump water through a membrane it would seem we have been hearing some erroneous info so far
these use a sintered ceramic media as their membrane (equivalent) The ceramic 'membranes' arent very permeable (extremely low flow rates by orders of magnitude lower) in comparison to the standard polyamide, polysulfone, etc. (actual) membranes.
 

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these use a sintered ceramic media as their membrane (equivalent) The ceramic 'membranes' arent very permeable (extremely low flow rates by orders of magnitude lower) in comparison to the standard polyamide, polysulfone, etc. (actual) membranes.
This may be true. But none the less if water hammer shock loading were a problem it could be neutralized using a simple pressure tank half filled with air to absorb the shock.
But a ram pump will only work if you have a proper place to install one. so probably not going to work on a boat.

But my bobbin dingy idea, now that's a starter.
 

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Once again, most boats spend most of their time at a dock, on a mooring or at anchor, where it is calmest. I'm not going to choose a rough anchorage a couple of days a week, just to run the watermaker rather than burn a gallon or so of fuel.
Thank for more info here sir :)
Blessing
 

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IIRC, the unit in MEN was a CINVA ram. Essentially, a turbine operating a (much) smaller volume pump. The more pressure on the vanes; the more water pumped.
Imagine, if you will.......
a small, tow-behind water wheel; like an old paddle-wheeler...running a pump that feeds pressurized H2o onto the boat...somehow ;) . Now you use another turbine/slave cylinder to turn that pressure into whatever ya want. Increasing the mechanical advantage and reducing the flow rate (however) , you could increase pressure to RO levels!?Strictly theoreticall; but it *might* work to get a few drops an hour??? ;)

Rube Goldberg....move on over! :D
 

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I doubt that you could achieve the required psi to force the water through the membrane - about 800 psi is required.
I am the operator of 2 different RO systems one on an 80 foot westbay sunship and one at a large oceanfront residence. if memory serves they both start producing at around 400 psi. the one on the yacht (60 gph searecovery unit) operates at 600 and the large home unit (6 gallon per minute) at 800 psi.
 
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