 Re: RO-Unit
No, I have this one http://www.airwaterice.com/product/RKT
At 3 months, I am still getting zero TDS. I don't know that an extra DI resin cartridge adds much if you replace the one you have when needed.
The fast flush valve some people like that. I don't have that but it does come with the auto shut off valve.
I have not had to change out cartridges yet but
This would replace all filters two times but the DI (not the membrane either) for $30...that would most likely be two years worth. http://www.airwaterice.com/product/FIL6PK
Or this one has all 4 cartridges for $50 http://www.airwaterice.com/product/FILTP
Oh yeah, I have the 75 gallon per day as it produces more pure water than the 100 gpd.  _________ http://www.3reef.com/uploads/BirdSig3.jpgI Love My Sig By John Hawkins!!!!!!!!!!!!!
Date Started 9/04 58 gallon Oceanic Tank, 20 gal DIY sump/fuge w/ Kent Marine Auto top-off, Air Water Ice RO/DI, 10,000 K 175 W MH, 2 VHO 03's 96W each, AquaC EV 120 Skimmer
80 lbs LR, DSB in FUGE, 1 - 2 " LS in tank
Black Brittle Star, Chevron Tang, Crocea Clam, red & green Lobophyllia, Frogspawn, Porites Frag, Caulastrea Frag, Green Ricordia, Asst. Zoas, hermits, astreas, stomatellas, fighting conch | 
