DIY Watermaker

[Tellie]

I might have access to an older 40" vessel in a few weeks if any of you home built guys are interested. It has an older membrane that produces but I'm not sure how well as of yet. I throw these things on e-bay every now and then but if anybody here might be interested,

[thatboatguy]

Hi Everyone,

I just found this thread. I know a few of you from other boards and probably from cruising. I have not posted here in a while... if ever. I did build a few watermakers in 08. Someone dubbed them "Frankenmaker" and the name stuck somehow.

The MK I View topic - Frankenmaker progress : Cruisers Forum : Latitudes & Attitudes Magazine

And The MK II View topic - Frankenmaker MK II : Cruisers Forum : Latitudes & Attitudes Magazine

The MK I only makes DC amps and water. It's on a boat cruising in Mexico making around 50 GPH. There have been some bugs but we are working through them and bottom line is that it's still doing it's job.

The MK II incorporates a refrigeration pump to pull down the plates in our freezer and refrigerator aboard Marquesa, our Freedom 40 Cat Ketch. As soon as I finish up restoring our main cabin I'll be back to work on that installation.

If anyone is contemplating diy watermakers I hope the information in those threads can be of some help. Just to be clear, I'm not in the business of making these comercially. Instead we are getting ready to cruise full time.

George

[SeaKing]

Originally Posted by thatboatguy

Hi Everyone,

Instead we are getting ready to cruise full time.

George

Ya'll still here..when is the D.day

[thatboatguy]

Hey Chester,

We are still here with a tentative cut the line date of April 24th. Still lots to do. We hope to just head south until it becomes uncomfortably warm (maybe Charleston?) and then slowly begin following the sun North for the summer, then South for Winter, Rinse and Repeat... etc etc

George

[offrd2001]

I found this home drawn diagram using google images. If anything, it just might get the creative juices flowing to create your own. The conversion of L --> Gal = a little over 26gph.

DAVE

[offrd2001]

to add to my post above, I thought it would be helpful to add the link. Sail World - Powerboat-world: Sail and sailing, cruising, boating news

[Tellie]

Originally Posted by offrd2001

I found this home drawn diagram using google images. If anything, it just might get the creative juices flowing to create your own. The conversion of L --> Gal = a little over 26gph.

DAVE

If you're serious about building your own I'd get a hold of Brent Swains plans. He's a member here and they're worth the small price to help you avoid the many issues that crop up when one tries this for the first time on their own.

[Yachts66]

I'm just starting to figure all this out myself and I'm wondering if any of you have tried or considered running the high pressure pump off a AC motor powered by a genset? I know Brent likes the belted off the engine routine, but I'm just not a fan of that. Also, does anyone have a good source for pumps and filters?

Regards,

TJ

[Microship]

Originally Posted by Yachts66

Also, does anyone have a good source for pumps and filters?

One pump available. I pulled an old ASC out of my boat, and currently have the pump/motor assembly on eBay. Crazy-expensive to ship (so a buyer in the Pacific Northwest would be great), though one fellow asked me if I would separate them and ship just the pump (yes). The item # is 130297832711

(Mods, hope this is OK in this thread; please just delete if not.)

Cheers,
Steve

[beau]

i got hold of a set of plans that used a cat pump. I bought two X 2.5 X 40inch membranes etc but have had a rethink on the high pressure pump.

I recently purchased a Kipor 2kva 240 volt generator (great unit) for topping up my batteries.
Using the Kipor for power, I have been thinking of buying a 240 volt Karcher type high pressure cleaner unit to supply the 800 psi.

Have any of you had experience with using these units for RO

[thatboatguy]

Two factors to keep in mind are pressure and flow. You need the flow to help strip away salt accumulated on the membrane and take it overboard as brine. For optimum pressure washing you shoot for different factors. Check with the manufacture of the membranes and then get yourself a pump that matches those needs.

George

[s/v Jedi]

Guys,

All the high tech of water makers is in the membrane. The rest is stupid simple. Of course a pressure washer works. It will work longer when all pump parts are stainless (not galvanized steel, not plastic etc.).

Once you have the pre-filters + boost pump + membranes + pressure valve + pressure meter + product flow meter + reject flow meter installed, you can experiment. What you need is a HP pump that can provide the needed pressure plus the needed gpm capacity. If you build from scratch, you need some rules of thumb. Let's take my 40 gph unit (which I use at 50 gph because that's what the membranes are rated for):

I use a 3-plunger HP pump coupled to a 1.5hp motor. With no pressure, the flow rate through the membranes -> reject is 4 gpm. With 45 gph product flow, the reject flow is 2 gpm, which is 120 gph. This relationship of 45:120 is roughly 1:3. So, for every gallon of product, you reject (at least) 3 gallons, or, in other words, 75% of intake water is used for cleaning the membranes. Remember that a membrane is a self cleaning cross-flow filter so you can go to 1:4 but not to 1:2. Just connect that pressure washer and slowly increase pressure and see what the meters tell you. When you reach 1:3 and the output is small, you need a bigger pressure washer or accept that smaller output.

I also shiver when people tell me they adjust for 800 psi pressure. That is wrong. You must adjust for the rated product-output of the membranes without going over a maximum pressure (800, 900, 1000 psi, whichever you feel is still safe, but not more).

The pressure needed for your rated output varies enormously. An example: for tropical (warm) salt water, you can reach max. product output at 700 psi, somtimes even less. If you put 800 psi on, you "overload" the membranes. In fresh water, the same unit will produce maximum output at 200 psi. If you go to 800 psi with fresh water, you will quickly ruin your membranes. In brackish water, you are anywhere in between. We are now on salt water but it's rainy season and after a lot of rain, I only need 600 psi pressure for full output.

You can also use a watermaker (a robust one) as your pressure washer with one extra valve after the HP pump (if you already have the fresh water flush valve, which all units have).

cheers,
Nick.

[Yachts66]

Excellent info Nick. How do you control the pressure? Do you have a variable speed motor or are you using a pressure adjusting valve? Ditto flow rate? I'm trying to get a visual image in my mind on how all these inputs are controlled.

Thanks,

Thomas

[s/v Jedi]

Thomas,

Okay, I assume lots of readers are overwhelmed by Spectra's with all the electronics, automatic rejects etc. so that it isn't clear how simple a water maker really is. There's no need to buy schematics for building one.

So let me try to describe it as simple as it is: my completely manual setup, as bought from Offshore Industries.

First, a thru-hull fitting with seacock and sea strainer, all 3/4". Next component is a Lexan filter housing. On it's input is a hosebarb fitting and a hose to your fresh water pressure system. When you have chlorinated water in your tanks (water from shore or if you add chlorine to your tanks) you put a carbon filter element in this housing to get rid of the chlorine, which hurts the membranes. On the output of the filter is a nipple and a 3-way valve. The filter connects to one input of the 3-way valve and a hose from the sea strainer is connected to the other input of the 3-way valve. So, this valve selects input of raw water or fresh water. The output from the 3-way valve connects to a boost pump. I am pro AC powered watermakers and a March A/C pump (submersible type with the red and white epoxy housing) is the best choice here, I recommend that AC3 model. Next item is two Lexan filter-housings in series, using a nipple to connect output of filter one to input of filter two. The boost pump connects to the input. First filter is course, like 25 microns and the second filter is finer, like 5 microns. These filters protect the membranes against anything that passes the sea strainer. The output of the filters goes to a high pressure (HP) pump. In this example, a 3-plunger CAT pump is great. I got lucky and have a titanium version. I have a directly coupled 1.5 hp motor on this pump.

What we have now is basically a pressure washer without the wand. So, you could fit a high pressure 3-way valve on the output of the HP pump to make it work as both a pressure washer and a water maker. For pressure washer, you feed it fresh water. You must use a hose + wand that can't be closed or you must install a pressure switch so that the HP pump switches off (March boost pump can run, it's magnetically coupled).

Back to making water: With the pump and motor described above, you can use 1 or 2 4"x40" membranes. Two will double your output (40-50 gph). If you want just one (20-25 gph) you can select a smaller motor. The high pressure housings for the membranes have two connections at each end. The center connection is high pressure and the outer one is no pressure, product output. If you have two membranes, you connect them in series. The product output connection on the side where you connect the HP pump isn't used so put a plug in there. Now, you have 1 or 2 membranes with one HP input and both a HP output and a product output. On the product output, you connect a nipple, 0-60 gph flow meter, nipple and a 3-way valve so that you can send the product water to either your watertank(s) or to a small piece of hose that you use to check/test the product. On the HP output, you connect a nipple, a T fitting with pressure meter and pressure adjusting valve, nipple, 0-6 gpm flow meter, hose barb and hose to discharge the brine overboard. I have a 3-way valve in that line too, which I can use to circulate through the system instead of discharging. This is used for cleaning procedures but I think a bucket works as well.

That's it! Where I wrote "nipple" I sometimes have a small piece of stainless steel pipe with flare fittings instead so that the components are easier to position.

Now the way to take it into service: make sure you have a lot of water in your tanks that can be wasted; fill HP pump with the cat pump oil; close the seacock, open the pressure adjusting valve (HP valve) all the way. Put all the filter elements in the housings. Tighten the carbon filter housing and the 25 micron filter housing but not the 5 micron one. Crank the input 3-way valve to the fresh water position just so that water comes in slowly. You will see the housing being filled. Some time later, the water starts filling the 25 micron housing. After that, keep your hands ready to tighten the 5 micron housing but wait until water starts spilling. Dry the spill while the water is pushing the rest of the air out of the system. It will pass pumps and membranes so soon you will see it in the reject flow meter. Make sure the output valve is to the test-hose and into a bucket because you don't want the product in your tanks for now ;-) When you see the water in the reject hose, you can open up the fresh water input all the way. As air gets out and flow increases, you should see the reject flow meter starting to register something like 1 or 2 gpm. As soon as it stops jumping (there's air as long as it jumps), switch on the boost pump. Check if it runs. The reject flow should increase. All okay, no leaks? Hold on (it's noisy) and switch on the HP pump. Check for leaks again. Now, slowly start turning the HP valve while checking for leaks. Bring the pressure up to 100 psi and let it stay there. Keep checking for leaks and keep an eye on the product flow meter. Water should already be passing to the core of the membranes and pushing any air out through the product output. Soon there should be water and bubbles in the product flow meter. Wait until the bubbles stop. Now, increase pressure slowly until you reach maximum product output flow which should be around 200 psi pressure. When all is fine, release HP valve, switch off HP pump, followed by boost pump, followed by input 3-way valve.

Ready for raw water ;-) Open the sea strainer and fill it with water. Close it and open seacock. Start boost pump. There is still air in the lines, hope that the boost pump primes and pushes it all the way through. Now, repeat like with fresh water, giving enough time for air bubbles to disappear before switching on the HP pump. Keep the pressure off until all air is gone, like 5 minutes or so. Slowly increase pressure, waiting if you hear air again. This time, you have to go to much higher pressure 600-700 psi before anything happens at the product flow meter. After 5 minutes, taste the product. When you think it ain't too bad, catch some in a glass and measure with ppm tester. Note the value in a log and check that the reject flow is at least 3 times the amount of the product flow. Note these values in the log too, plus the pressure. If you really want it complete, measure the raw water temperature (outside the boat, before it enters the system) plus the product temperature. All these values will later indicate if there's a problem.

The ppm value should improve after some use. Check that. After 50 hours you need to change the oil in the Cat HP pump (break in). Check for metal flakes in the oil. Next oil change there should be less to none.

cheers,
Nick.

[Boracay]

At my stage of fitout I don't want or need a watermaker, but it sure looks like some thought into where it might go is needed.

Assuming it's needed every couple of days what sort of access/mounting is good, and where is the best spot to put everything?

Space runs out very quickly, even on a 44' boat!