Steer clear of almost all e-bay RO/DI units, they are cheap for a reason and the reason is quality and performance. ANY and I repeat ANY RO/DI unit should give you a 0 TDS reading after DI, but for how long. Cheaper units use lower quality membranes, in some cases they are not even true 98% rejection rate 75 GPD RO membranes but are 90% rejection rate nanofilters not even approved for drinking water quality systems. Most of them don't use true RO filters but use a little hollow clear tube with a little bit of DI resin bobbing around in it, that is not a DI filter. DI filters are a standard 10" canister with a refillable cartridge inside that holds a full 24 oz of DI resin.
Please do your homework and don't get caught up in the 0 TDS argument. Ask them to tell you who makes the membrane, is it a 75 GPD Dow Filmtec, is it ANSI/NSF approved for drinking water and not pool and spa use, does it have a 24oz vertical DI, does it have a 1.0 or better yet 0.5 micron carbon block and no granular carbon, I can list dozens of things that make up a high quality RO/DI system.
You will spend a minimum of $149 for a good reef quality system, $199 to $250 for a little bit better one with a good TDS meter and pressure gauge and probably an autoshutoff valve and $349 for the absolute best unit available today with everything you would ever need and greatly extended filter life.
You have already been given three good choices in AWI, Filter Guys and Buckeye and add
www.spectrapure.com to the mix for the MaxCap RO/DI system.
