Generally with RO/DI you get what you pay for, chep units use cheap components and higher priced units (within reason)use quality components. Things to look for are Dow Filmtec 75 GPD true RO membranes. Watch out for vendors that say things like "Made with Dow materials", "Made in USA", "Better than Dow" and numerous others. Some vendors sell units with Chinese or Taiwanese knock off that are not even ANSI/NS approved for drinking water in the US. Others use 100 GPD nanofilters which are only ANSI/NSF approved for "Pool and Spa Use" and not for drinking water. Generally these are only 90% efficient instead of 98% efficient. The reason the 8% difference is important is for every
2% increase in RO efficiency your DI resin life
doubles, so an 8% increase adds up to huge $$$ savings in DI cost in a very short time.
Look for units that use solid carbon blocks in a low micron range of 1 micron or less as they have the greatest chlorine and volatile chemical adsorption. Some vendors use blocks of unknown micron size which is a red flag, or they use cheap granular activated carbon which may only adsorb the chlorine from 100 or 200 gallons of water instead of 20,000 gallons for a 0.5 micron block.
Look for features like an inline pressure gauge and a good quality handheld TDS meter, you will need both to monitor the efficiency of your unit and help determine when things need servicing.
Most importantly look for one with a standard 10" vertical canister type DI filter as these hold 24 oz of DI resin as opposed to some e-bay type units with horizontal clear tubes that hold 6 oz of resin bobbing around in them. Vertical filters are much more efficient especially if the cartridges are hand packed so water does not channel or short circuit which is common in horizontal tubes, water is going to take the path of least resistance which means it does not come into contact with all your DI resin.
There are several vendors that are RC sponsors including
www.spectrapure.com ,
www.thefilterguys.biz ,
www.purelyh2o.com and
www.buckeyefieldsupply.com .
Air Water & Ice has always been good as some have already pointed out and Melev builds a pretty good unit but he does not use the Dow Filmtec membrane which I feel is better in this application.
My personal unit is the new Spectrapure 90GPD MaxCap RO/DI system which is the absolute top of the line for only $269 right now on an introductory special, it cannot be beat at any price in my book.
Carl
