How Often Should I Change My RO & DI Cartridges?

When you start detecting more chlorine in the waste water it's time to change the carbon. When pressure drops to your RO from normal, change sediment. Change the DI when your TDS rises in the good water. RO membranes should last you many years if you maintain it, flush them, and keep chlorine away from them because it will oxidize them.

RO Membrane - Change when rejection rate gets down to 96%, or you experience a decrease in psi.
Sediment - Change at 6 months or if psi decreases, whichever comes first.
Carbon - Change at 6 months or if detectable chlorine, whichever comes first.
DI Cartridge - Change when tds reaches 1