Water in the Pacific

[owly]

Originally Posted by lizardofoz

Hello HW,The HP pumps do not like running under a specified RPM or run to fast so there is a window of adjustment only. I would be interested as you have recommended that people build their own so they have regular components in there that can be sourced from the manufacturer rather than the " company that assembles them and calls them their own" Have you done this yourself? Had a good result? I am interested to know the cost of setting up a RO system. I have done this many years go with components myself. To far back to remember exactly but i could estimate. Be interested to see how someone else did it. Good for all the people viewing to also know.

I bought a Cat pump for my home made kit. Had a local shop make up a pressure guage and flow meter arrangement. Bought local HP housings made in Thailand and imported membranes 40" long and had a local hydraulic shop make up the HP hose same as they use for diving compressors. Mine was run of a clutch of one of my main engines

The plunger pumps like the Cat pump you used do have a considerable range below their max RPM. These are basically pressure washer pumps, and while many people use the expensive stainless steel versions, the brass head versions are also used and people claim they hold up well. The head itself is merely a block of metal drilled for the plungers, which are ceramic, and machined to accept the seals the plungers run through. Threaded caps contain intake and exhaust reed valves, which consist of plastic or metal cages containing a stainless steel spring and disk. If the cages are metal, they will usually be brass. Considering the fairly frequent usage and back flushing the filter with fresh water using the pump, corrosion should be of minimal concern. Teardown of the valve assemblies amounts to nothing more than removing threaded plugs, which is easy. I recently ordered a complete valve rebuild kit for a General pump that runs on 1.5 HP. It included caps..... I had one broken cap and a kit was the only way I could order the cap. Cost about $100. For a watermaker, this pump would put out a bit under 2 gallons a minute at 1000 psi on one horsepower.

Cat, General, and Hawk (Hotsy) are the best pumps imho, based on many years of experience with high pressure washer pumps. The quick and cheap solution however is just to go out to Harbor Freight and buy a $99 pressure washer, and throw away everything but the pump and motor. 1.3 gpm @ 1750 psi 13 amps. Your pressure will be about half that..... pressure is governed by restriction, which is the filter resistance. Rig a pre-filter and screen with a separate low pressure pump to feed the prefilter and the high pressure pump, and whatever you want in the way of valving for back flushing, gauge and control panel, etc. I would not want a continuous brine bleed, as high pressure flows use a lot of horsepower. Flow * pressure / 1710 equals horsepower, and a bleed at 1000 psi is very inefficient. Better to periodically cycle... high pressure RO cycle followed by low pressure brine flush using seawater from the low pressure pump to flush out concentrated brine at intervals. A membrane and pressure vessel can be had from a number of sources, and there are quite a few articles and Utubes on DIY watermakers. One particular cruiser who does Utubes.... Emerald Steel, has had their home made watermaker in service for quite a few years with almost no maintenance. It's not rocket science. I believe a resourceful cruiser could make a completely serviceable watermaker for close to $1k. A hundred dollar pressure washer as the heart of a watermaker is a throw away item.... You can well afford to carry spares. If you decide you need a $1500 dollar pump and motor later, you really haven't lost much of anything in the meantime.



H.W.

[owly]

I just discovered a thread in which another member has built a watermaker using a cheap pressure washer for the pump, and has been cruising the Med with it successfully.



H.W.

[Jimmyhenry]

Can you do it - definitely.
Would I not have a WM. Definitely not.
One expedition ashore topping up water tanks using bottles will convince you.
Vanuatu is very limited in easy water supply.
If you chose to go without a WN I recommend you use a pre filter for water. We use a .5 micron filter for all external water going into our tanks. We also have ano .5 micron on after the cold water supply pump. Don’t really need this but it certainly makes drinking straight from the tap very acceptable.
I would recommend going 12volt. That way you have more options on running the WM.

[Mr B]

I had a little wonder, WM, 160-200, The motor in it died after getting drowned,
$800-00 to repair mine or $1100-00 for a new one, 12 volt motor,
I bought a ten HP petrol water pressure washer unit, $340-00 Delivered,
Bought a couple of stainless fittings for it to connect to the Little wonder WM and it works fine,
It puts out 3800 PSI, at about 1.8 GPM,
I have no idea yet on how much fresh water it will make,
The pressure pump part is Brass, They are $90-00 for a complete replacement, So its a throw away item if it carks it,
Readily available, By Post,
I did have to modify the exhaust to quieten it down,
I dont like petrol on my boat, But I carry petrol for the outboard, So a bit more wont worry me,
I am using the Little wonder pressure gauges to restrict the pressure to 900 PSI,
All I have done is bypassed the 12 volt motor and pressure pump of the Little wonder unit, Every thing else is just the same,

I watched a video on youtube on how to build my own water maker, This is the result of that video,
I did this because my invertor wont run a 2000 watt electric motor,


Cheers Brian,

[westsailwill]

Originally Posted by Pelagic

I think it can fairly be said that we adjust to "complexity" all the time. Its called progress!

When liveaboards adopt a system as a worthwhile inclusion into their limited space....and...then years later......replace it with a new better one after its design lifespan has expired....it is because they believe that equipment has made their life more convenient and less complex.

Hauling dubious water or buying local meats in a fly infected market, or simply doing without both for long periods is a lifestyle choice just as foregoing onboard internet, so we can research and share opinions.

All can be called complex. The study of meteorology is complex. Being your own wilderness doctor or plumber is complex.... UNTIL you learn the basics and gain experience/confidence in maintaining those systems.

MTBF (Mean Time Between Failure) on proven systems these days are counted in years, which is a standard I can aspire to for unlimited water and my frozen favorites.

Very well said

[a64pilot]

Lizardofoz,
Your saying a Rainman can make 40 gls of water an hour with a 1000W generator, or did I misunderstand?

[kmacdonald]

Originally Posted by owly

I just discovered a thread in which another member has built a watermaker using a cheap pressure washer for the pump, and has been cruising the Med with it successfully.



H.W.

I've seen that article. Don't think you can build a half decent watermaker for less that $2500 and that would require resourceful purchasing.