I just got an RO/DI system from bulk reef supply (about a week ago) and about 1/5 of the DI resin is already brown. The TDS in hovers between 500-700, the RO out is about 30, and the DI out is 0. How long does DI resin usually last in the Cedar Rapids/Iowa City area? How often do you flush your RO membrane? How often do you replace you sediment filters and carbon filters? How often do you replace the RO membrane? The way it's looking, I'll be replacing the DI every month! The sediment and chloramine/carbon filters look like they should last about 6 months while I've read that the RO membrane should be replaced every year. I'm just trying to get a handle on what's going on here. I've heard of people going 4 months without replacing their DI resin. I lose about 20 gallons of evap per week and do monthly 20% water changes. So that's about 1200 gallons a year.