Watermakers: is there a cheaper alternative

[GrowleyMonster]

A solar still is a marvelous idea! If you cool the condenser surface with ice (you DO have an icemaker, right? One mustn't live like a savage, after all!) you will find a solar still works great, I think.


Seriously though, I,too, would love to see an affordable and efficient RO watermaker that makes 2 or 3 GPH. It ain't happening any time soon, though. Maybe someone could hack something together using one of the hand pump type membranes? The regular RO membranes just don't work well below their rated pressure and volume.


I bought a used system and it was reasonably priced because the PO wanted to switch to a 110 system and double membrane. Keep an eye out for used brand name equipment. Don't buy a used system with a power washer pump. These pumps are cheap but they don't last very long with seawater. Cheap enough to keep a spare or two aboard? Maybe. YMMV. I will be home in 10 days and one of my 1001 projects will be to install my new to me watermaker and test it with the old pickled membrane. It is coming with a new membrane, too. I don't remember the particulars. Bought it months ago but I haven't been home and haven't even seen it yet LOL! Life at sea sucks like that sometimes. Anyway, there is no practical RO system currently available for low volume production. For a small boat where a typical RO watermaker is not possible or practical, increase tankage and figure out how to best capture rain water. A hand pumped system might be a good backup, depending on where you are going. Some places it just doesn't rain.


A survival type solar still typically produces ounces, not gallons, in a day in the real world. Enough to make dying of thirst take a little longer LOL. And on a cruising sailboat they might be in the way anyhow. In a calm protected anchorage you could probably float a few around the boat, though. An engineered solution for someone who motors a lot would use a heat exchanger to heat water, and a vacuum pump to pull a vacuum on the hot water to boil off water vapor, which then would be condensed. Such an evap system could be fairly efficient. That's how water is made aboard ship. Not sure but I think we max out at around 80 tons per day of fresh water production. Main engine is the heat source.

[motion30]

Seawater pro. $1500

[thinwater]

Originally Posted by Chotu

I'm my humble opinion you are on the wrong track.

You don't need a watermaker at that usage level. You need to improve the tankage on your boat. There are many places on any boat that can be dedicated to extra water storage.

How long do you want to be able to go without getting water?

What he said, plus a few more possibilities:

• Collect and treat rainwater. A good system can be built for $50 + the catchment. 50 ft^2 will get you 2-5 gallons per day average with typical rainfall.
• Distillation. It's pretty easy to rig up a still that sits on the stove, but the fuel will be about 10% of the water generation. A pound of fuel should produce at least a gallon of water.

Taken together (with the above ideas) you should get there for well under $1000.

[Matt Johnson]

Originally Posted by billdomb

OK; some basics.

What PRESSURE is needed to feed the RO membrane?

3000 PSI?
5000 PSI?

Pumps generating these pressures are pretty inexpensive, methinks.

You'd need the membrane cylinder itself, of course, and would do well to have a little prefiltration before the pressure pump. Ought to be pretty straightforward cobbling together a functional system.

600-800 psi (with closer to 800 being more normal).

Matt

[GrowleyMonster]

Originally Posted by motion30

Seawater pro. $1500

Uses pressure washer pump. The pump won't last long. However the pump is cheap enough to regard it as a consumable, along with the membrane. So, YMMV but you can hardly DIY a system for less than that. I say it's a buy, for many sailors. Run it off the main engine or the generator and you can charge batts and make water at the same time and share the overhead between the two tasks for a small increase in efficiency. The diesel burns some fuel just to run with no load and with a load, some of the energy consumed just turns the engine. The lower the load, below a certain point, the higher percentage of fuel is used just by the diesel to sustain itself. Increase the load and a smaller percentage is wasted.

[RaymondR]

I wonder what you could do with a solar still if you made the evaporator with a glass top, black metal mesh bottom, mounted it like we do solar panels and placed a vacuum on it to assist with the evaporation?

[mrybas]

Originally Posted by Cheechako

This is your answer. Simplicity is your friend. I made mine out of a used 120 volt watermaker. I scrapped the big electric motor and the complicated electronics panel. Mounted the Cat pump on the boat engine, had to buy a 12v clutch. I used a needle valve and a brass pressure relief valve and a good gauge. It had 3 old membranes, I went down to one membrane (new).
-Start engine
-activate the clutch
-look for water flow on the overboard fitting
-Adjust needle valve to 600-650 psi on the gauge
-make water.

I made 20 gal an hour.

Do you have anymore info on your system? What is a cat pump (high pressure pump)? What is involved in mounting the high pressure pump on the engine? The 12v clutch engages the HP pump when the water maker is turned on? The needle valve is used to adjust pressure to the membrane? Any photos?

[skipgundlach]

Originally Posted by Mike OReilly

Simi, can you outline your collection system. I’ve been half-heartedly pondering some sort of rain collection system for a few years now. After collecting, what do you do (if anything) for filtering before the water enters your tank?

Here's ours:

Pictures: Flying Pig 2013-2014 Shakedown/Catch Rain

[skipgundlach]

OP, a guy in the Vero Beach City Marina has what you want.

John, on NonLinear (for some reason I have lost BOTH his cards, recently acquired, yet) has one he's selling for $500. Assuming I will find him at some point (either here in person or his card or on the morning net) I'll point him to this thread.

He's getting off the boat after many years and is fairly well known in the cruising community...

[Q Xopa]

Originally Posted by GrowleyMonster

Uses pressure washer pump. The pump won't last long. However the pump is cheap enough to regard it as a consumable, along with the membrane. So, YMMV but you can hardly DIY a system for less than that. I say it's a buy, for many sailors. Run it off the main engine or the generator and you can charge batts and make water at the same time and share the overhead between the two tasks for a small increase in efficiency. The diesel burns some fuel just to run with no load and with a load, some of the energy consumed just turns the engine. The lower the load, below a certain point, the higher percentage of fuel is used just by the diesel to sustain itself. Increase the load and a smaller percentage is wasted.

He also sells other pump options including high quality ones. Chose which one you want.

[Mike OReilly]

Originally Posted by skipgundlach

Here's ours:

Pictures: Flying Pig 2013-2014 Shakedown/Catch Rain

Thanks for this Skip. Perfectly simply. Love it. On my boat my deck fitting is actually elevated above the deck level. It makes using the dam approach harder b/c I have to elevate the water level even higher. But it’s certainly worth a try.

[skipgundlach]

Originally Posted by Mike OReilly

Thanks for this Skip. Perfectly simply. Love it. On my boat my deck fitting is actually elevated above the deck level. It makes using the dam approach harder b/c I have to elevate the water level even higher. But it’s certainly worth a try.

FWIW, we do not treat rain water (which we only collect in the Bahamas, the only other place we tried it tasting horrible by comparison) but we do scrub the deck and let it rinse before opening the fills...

[thinwater]

Originally Posted by skipgundlach

FWIW, we do not treat rain water (which we only collect in the Bahamas, the only other place we tried it tasting horrible by comparison) but we do scrub the deck and let it rinse before opening the fills...

Pre-filtration, followed by chlorination/dechlorination really helps with both safety AND taste. This is how municipalities treat drinking water.

[thinwater]

Depending on the specifics of the deck, an old bike innertube filled loosely with aquarium gravel (or similar) with the ends sealed is really handy. Unlike rags, if doesn't blow away. Worked great for the gutters on my PDQ. Do NOT overfill; that makes it stiff.

[sparrowhawk1]

I just updated my rain catching on the thread Raindrops Keep fall'n On My Head. Take a close look at the bucket and you will see a lot of sediment so do not let rain go directly into your tank.