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I spent quite a bit of time researching sources of reverse osmosis parts but even more time figuring out exactly what I needed. THere are a number of sources on the web for membranes and pressure vessels and the prices are fairly close. It does pay however to do some price shopping though. By checking around I found a variation of almost $200 for a pair of vessels and membranes. If you have a lot of patience and know exactly what you are bidding on you can find soe bargains on Ebay when it comes to pumps, meters, guages and stainless fittings.
Let's start with the most expensive single part, the high pressure pump. It should be rated at about 1200 PSI and 3 to 4 GPM for most RO systems between 20 and 40 GPH . It should also have all stainless or nickel aluminum bronze wetted parts to stand up the the high pressure seawater. While regular pressure washer pumps are a lot less expensive they do not make very good RO pumps. They have several problems. First, while they may have stainless cylinders but the manifolds are cast brass. Then they are designed for 2500 to 4000 PSI and will waste a lot of energy trying to run them at lower pressures.
My first choice was the CAT 241 an all stainless plunger pump rated 1200 PSI maximum and 3.6 GPM at 1750 RPM. IT list for about $1,800 and the street price is about $1,300. THe Cat 247 is the bronze model of the same pump Almost as good and about half the price. Both are intended for belt drive but can be addapted to direct motor mount if you want to go 120VAC. Here is the data sheet for the 241/247. The CAT 2SF25SS is a 1200 PSI triplex pump that delivers 2.5 GPM and is direct motor mounted. It could be mounted on a 1 HP Leeson 12VDC motor but it would eat a lot of amps. EDI Distributors had the best prices on all Cat Products including the pressure regulator and the electric clutch.
Another all stainless pump that is used by several direct drive RO brands is the General Pump WM series. They range from .5 to 4.2 GPM at 1500 PSI. Prices range from $450 for the small one to $800 for the 4.2 GPM model but they cannot be belt driven verey easily. Pumps-Direct had the best prices I found fot General Pumps.
Pressure Vessels and Membranes
I found the best prices on pressure vessels at Pacific RO. They say they are wholesale only but if you order two they will consider that "wholesale". They sell membranes too but check around. I have pretty well settled on Dow/Filmtec membranes. Their recovery rate seems a little higher and the Filmtec documentation and tech support is the best. Applied Membranes occasionally has better prices. Another is KFS Pure Water Systems.As of this writting American RO Systems had the best prices on SW30-2540 membranes. (The web page list them as 4040 in error. Check the dimensions column).
Flowmeters
Finding the right flowmeters was aharder than I thought. They need to be small enough to not take up to much real estate on the panel but large enough to be easily read. The ranges had to be where the 40 GPH product and 3.2 GPM of brine would be about mid way on the scale. After screwing around with several flowmeters on Ebay I finally bought exactly what I needed from Dwyer Instruments. Not all that expensive either. After talking to their tech support and looking at all the specs I decided on the 4" scale Visi-Float acrylic flowmeter. These are machined from a block of acrylic and are just the right size to fit on the panel without taking up to much space and still give good resolution. The brine meter is a VFB86 that measuers from .5 to 5 GPM. The product meter is a model VFB81 that measures from 6 to 60 GPH. With a ratio of 5:1 the proper recovery rate will be almost exactly even on both meters making setting easier. Here is the Spec sheet (PDF).
Front Panel Express
Hanna TDS Meter.
PCB Express
Other Stuff
You will need a lot of high pressure fittings and hose. When you are working down a long list of hardware and fittings the best frustration preventer on the web is McMaster-Carr. Sometimes their prices are a little higher but they have everything and delivery is usually within 48 hours. Same with electronic components. In my opinion Digikey has the best web site for ordering almost any electronic part. The prices are usually very good (ALWAYS lower than Radio Shack but you may have to buy a pack of 10 pieces when it comes to resistors and capacitors. Still 10 resistors at Digikey cost less than 3 at Radio Shack.
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