Selecting a pump for watermaker diy

[offgridcanuck]

We are starting our watermaker build. We have Swains and Nigels books showing some possibles.

We are going to use the one of these from americanro dot com:
62. SW30-2540 2.5 x 40 800 700 99.4 $180 $170 $160 $155 63. SW30-4021 4.0 x 21 800 800 99.4 $290 $285 $280 $275


















So we are looking for a t911 or like pump that will do 800psi at those flow rates. We have a 2k inverter on the boat or a decent amount of dc power and 1k solar. I am heading towards the dc power pumps but maybe I am wrong?

Hoping for some opinions on which parts to oder for the pump side. We can go smaller on the membrane and output if it will fit into our DC easier.

thanks!

[ColdEH]

If you have a generator on board you would be best to belt a Hydracell D10 off of that . Pumps are what breaks most on a water maker. Get the best one you can . Piston pumps like Cats always put a little bit of oil in the water before it gets to the membranes, it's the nature of the design, just like a bit of oil gets past the pistons in your car engine. The worst enemy of a membrane, is oil. The oil in a Hydracell D10 pump is totally separate from the water. But you will need some umph to power it and a DC motor just wont do it . If you increase your power by using an engine to drive the pump you can shorten the time it takes to make water . 40 gallons in around an hour with two 40 inch membranes should be within reach , the pump will last forever .
Take a look at mine
Hydra Cell D10 Pump for Watermaker

Regards

[offgridcanuck]

I picked up a 110v 12amp motor attached to a HRO CAT pump and a 40 inch membrane housing plus some odds and ends as far as valves go.

The guy who sold it to me showed me the one he cobbled in his boat. He had a primer pump go through a flow rate and into a 30 and 5 micron filter, oil water sep and then into the main pump. Looks like a diverter which led to his head sink to test the product before switching it into the main tank. There was a valve (needle??) and then a pressure gauge after the cylinder?

So my question is now, is that just a needle valve that controls the exit pressure? Does anyone have a simple diagram of this? I assume between main pump and membrane I should run hard stainless line to hold the pressure?

I have found membranes super cheap at
Wateranywhere.com

Order one and a spare I guess?

[phorvati]

Yes the needle valve controll the pressure. mine is manual stainless and i turn it sligthly to build working pressure. It takes couple of turns but its very sensitive. Most people put bypass regulator at the pump in case there is a clog or accidental buildup of pressure. These are simmilar to the ones on pressurewashers but they should be stainless.
Ive had rubber pressure washer hose with swagged stainless 3/8" NPT male fittings built by an online shop. I found that stianless high pressure hose you get on mcmaster was developing pinhole leaks if bent close to maximum radius. Not sure why. I still use them between membranes and from membrane to needle valve. My pump is engine driven and its about 10 feet to the membranes. Consider plumbing your membranes in parallel. I put a 3/8" tee before the membranes. Then 1/4" tee after to join the flow before going into needle valve.

[foggysail]

Originally Posted by phorvati

Yes the needle valve controll the pressure. mine is manual stainless and i turn it sligthly to build working pressure. It takes couple of turns but its very sensitive. Most people put bypass regulator at

A needle valve works as long as the pump's flow rate is constant. Vary teh pump's RPM and so will the GPM vary.

[phorvati]

Originally Posted by foggysail

A needle valve works as long as the pump's flow rate is constant. Vary teh pump's RPM and so will the GPM vary.

Since I am using the needle vale i always think in terms of RPMs vs pressure. I have to keep RPMs constant while making water. This is the downfall of using needle vale. Any increase in RPMs will translate into increase in pressure as your flow is fixed by the needle vale. So on an engine driven pump, I have to keep my engine in neutral when making water. This system only makes sense if you have large capacity membranes. I make my water in about 2 hours. That lasts me a week, so idling the engine for about 2 hours per week is negligible. The benefit of using the needle valve is that its cheap and simple.

[ColdEH]

Get yourself one of these,


Wanner Model No C22ABBNSSEF Bypass Pressure Regulating Valve Unused in Plastic | eBay.

Keeps your pressure in a good place

Regards