When do I replace R/O Membrane?

1st stage:  high capacity, 5 micron sediment filter, to remove sediment, rust, sand, (replace every 12 months)

2nd stage:  high capacity carbon filter, coconut shell carbon block filter removes chlorine, taste & odor (replace every 12 months)

3rd stage:  high capacity carbon filter, coconut shell carbon block filter further removing chlorine to ensure 100% removal of chlorine (replace every 12 months)

4th stage:  TFC-100/TFM-100   Premium membrane we have done extensive testing among different brands of membrane, and we recently have switched to a higher rejection membrane GE Desal membrane, (even better than Filmtec membrane), it removes 97% to 98% of all chemical, dissolved solids in tap water. (replace every 2-3 years) Look at data below.

5th stage:  DI filter (de-ionized, de-mineralize filter), Nuclear grade, color changing DI filter with refillable clear housing.  The DI filter removes remaining of dissolved solids after RO system.

6th stage:  DI filter (de-ionized, de-mineralize filter), Nuclear grade, color changing DI filter with refillable clear housing.  The DI filter removes remaining of dissolved solids after RO system. A ball valve is included for dispensing DI water into open containers or to open tank.  GOOD for reef, aquarium, hydroponics applications.