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**weavis** · 19-04-2014, 18:04

So the average required pressure for forcing water through the membrane to remove sodium chloride is 68 bar.

hmm.

I think, I will have a look at the pump mechanism of an espresso coffee maker. If water can be de-salinated when hot, then that is a mechanism that will do it. If you boil water and use the heated water pressure through the pump, then 100 bar is easy to achieve.

hey! I like coffee. Sue me!

Yes it would require a heat source. Perhaps gas rather than electric. And it will make 8-10z a minute.

colemj · 19-04-2014, 18:37

Quote:

Originally Posted by SV THIRD DAY

I love it...tie my rocker stopppers into powering a water maker pump....
We BOTH may have already had too much wine today...

I guess that cuts out the multihull market…

Mark

FlyingCloud1937 · 19-04-2014, 18:38

Just remember, salt precipitates into crystals at about 130 F.

Lloyd

Quote:

Originally Posted by weavis

So the average required pressure for forcing water through the membrane to remove sodium chloride is 68 bar.

hmm.

I think, I will have a look at the pump mechanism of an espresso coffee maker. If water can be de-salinated when hot, then that is a mechanism that will do it. If you boil water and use the heated water pressure through the pump, then 100 bar is easy to achieve.

hey! I like coffee. Sue me!

Yes it would require a heat source. Perhaps gas rather than electric. And it will make 8-10z a minute.

Phantoms · 19-04-2014, 18:55

Quote:

Originally Posted by weavis

So the average required pressure for forcing water through the membrane to remove sodium chloride is 68 bar.

hmm.

I think, I will have a look at the pump mechanism of an espresso coffee maker. If water can be de-salinated when hot, then that is a mechanism that will do it. If you boil water and use the heated water pressure through the pump, then 100 bar is easy to achieve.

hey! I like coffee. Sue me!

Yes it would require a heat source. Perhaps gas rather than electric. And it will make 8-10z a minute.

Why not just make a desalinating still? No need to force the water through any membrane.

hellosailor · 19-04-2014, 19:04

One might wonder if the typical RO membrane would be terminally insulted when fed a diet of boiling water.

After all, even common household water filters are not rated to work in "hot" water lines at household "hot" temperatures of 120-180F. (Most codes set a max around 125F IIRC now.)

SV THIRD DAY · 19-04-2014, 19:08

Quote:

Originally Posted by hellosailor

One might wonder if the typical RO membrane would be terminally insulted when fed a diet of boiling water.

After all, even common household water filters are not rated to work in "hot" water lines at household "hot" temperatures of 120-180F. (Most codes set a max around 125F IIRC now.)

We had a client hook up his fresh water flush to his HOT water line rather than his cold water line. Melted his RO Membrane....and no, that wasn't covered under Warranty...but he DID ask....

**weavis** · 20-04-2014, 04:24

As originally stated, I just noted the pressure required for pushing through a membrane. I have no experience with the extraction process itself.
If heat is a no no for the membrane....Then I guess its just a basic distillation process that is required.

I was not sure whether sea water could be distilled easily and it turns out, it is very easy. A little read on the subject and a look around the internet showed that there are any amount of units available for this process, including some solar stills. One guy even used a fresnel lens for heating the pot!

I imagine its a high energy usage conversion ratio to get the end product. Yet in saying that, the reality is that its basically a vessel for holding water, a condensation unit, some tubing and a heat source.

The ongoing cost is the heat source. With a little thought and application, even this might be overcome to make a cheap unit.The whole unit could be integrated into a hot water/ heating system for the boat and also produce distilled water.

I have use of an electric water distiller and a copper distiller...... it is illegal to make alchol without a licence.......... but it does distill water efficiently.

I have never tried salt water, and never will with these units.

If a membrane costs $200 then a person could use a lot of propane and make a lot of water for that.....

Phantoms · 20-04-2014, 07:28

Quote:

Originally Posted by weavis

If a membrane costs $200 then a person could use a lot of propane and make a lot of water for that.....

Add in the cost of a water making RO system and you could buy quite a bit more.

SV Windrush II · 20-04-2014, 09:28

Very interesting guys :thumbup:

Sent from my SGH-T999L using Cruisers Sailing Forum mobile app

Zanshin · 20-04-2014, 09:38

Weavis - remember that only a small percentage of that hot water actual gets to become sweet water, most of it is bypass water and is ejected overboard! So a typical 20% recovery ratio means you've heated 80% of your water for naught.

nimblemotors · 20-04-2014, 10:05

A good approach is to use a solar water heater to raise the input temp, but the limit is about 100F, so some complexity to regulate the water temp. Worth it though, because the higher temps require less pressure == less pump energy used.

exkma367 · 20-04-2014, 10:46

We made our own engine driven watermaker, and ran it off the old atomic four.

We used a General TT911 pressure washer pump, I picked up for around $250.00. We flushed it with fresh water after every uses and had no corrosion issues. Ours was very simple. No clutch. We just put the belt on when we needed to make water. I added a 4 inch pulley to the front of the crankshaft, (we made our own adapter but Moyer Marine can hook you up with one). I also put a 4 inch pulley on the pump, and welded up a bracket that held the pump over the area of the starter. I used swagelock fittings and stainless tube for the high pressure lines and plastic tubing on the rest. We used a waterpuppy 12volt pump to keep her primed. From the waterpuppy she was plumbed to two prefilters. If I remember right they went from 30 microns to 10 microns. A stainless high pressure regulating valve, and couple of gauges to monitor the pressure and flow of the brine and product water. We used one 4025 fiberglass pressure vessel and membrane and got 15 plus gallons per hour. We plumbed in three way valves to divert the product water from a spigot on the sink and the main tank.

To make water we would put the belt on the pump, flip the switch on the primer pump, start the engine, and adjust the engine rpms, being carefull not to over rev the pump. With the 3 way valve turned to the sink, I would adjust the pressure valve until the high side showed 800 psi, and the product flow was between 15 and 18 gph. By the time I made it to the sink to taste the water, it was always sweet and salt free, I would then turn the valve to tank and fill her up. When done I would fill a two gallon bucket with product water from the sink and then put a flush hose into the bucket. The flush hose was hooked to another three way valve before the primer pump. I would turn the flush valve and let it suck clean water until almost empty and then shut down the motor.

The only problem we had was a bearing that went out in the waterpuppy primer motor. I now have a half dozen of the cheap bearings as spares.

I cant tell you how much the system cost, because I was afraid to add it up. The big items are the pressure vessel, pump and regulating valve, but there are deals around if you have time to shop around.

I also know you can buy a lot of water for a thousand dollars. You can decide if my system seems like more of a hassle than loading jerry cans into the dingy and going in search of agua. We were a small boat with not a lot of tankage so it worked for us.

socaldmax · 20-04-2014, 11:08

Quote:

Originally Posted by s/v Beth

Rich, you have one of these. Is the hand pumping by compressing the lever towards the membrane? Does it spring back or do you have to force it up too? Seems like you could put it on a wheel mechanism attached to a couple of pedals....
Anyway, got my work cut out for me. I will not beat this dead horse further. My wingman and I will discuss it over a meal at Nanaimo.

The only way to do it reasonably cheap is to get incredible bargains on the parts required. There is an Ebay seller selling the Pur Suvivor 06-LL for $100 ea. They were in storage, might need a new membrane or just serviced. It looks like those sell for $995 ea new. If you bought 2 of those and somehow rigged those up to a stair stepper, you'd be into all of the major parts for only $240 instead of $2030.