[mike31154]

From what I've read here on the forum, you folks on the west coast & the island have very low TDS right out of the tap. Since you're still in the planning stages, probably the best thing to do is spend a little money on a TDS meter and perhaps a pressure guage. Check your tap water TDS & water pressure, then you'll have a better idea of what you need as far as stages etc. If your source TDS is 10 or lower, it may even be more cost effective for you to simply get a large DI stage. This has the advantage that you won't have any waste water as is the case with any RO system. Or you might go with RO and no DI stage. My source TDS is 210 & according to the TDS meter, my 75 gpd membrane gets that down to 1 and even 0 TDS after about 5 minutes of running. More than two years after installing the system I'm still on the original DI media.

After that, most systems regardless of who makes them are made up of more or less generic components. The costly item is the RO membrane and you want to make sure that's a good quality one. 75 gpd units have a better rejection rate than 100 or 150 gpd units. Some of the cheaper systems will have no frills, that is, no TDS meter, pressure guage, auto shut off valve and may have lower quality JG fittings, lousy pre filters & carbon block as well as white pre filter housings vice the clear ones. Expect to pay at least $200 for a decent 4 or 5 stage system. You may be able to get away with a 3 stage (sediment pre filter, carbon, RO) if your source TDS is as low as most folks from the west coast report.