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
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.