Sediment Pre-Filter - Change every 6-12 months (more often in areas with very high sediment in the water).

Carbon Post-Filter These filters should be changed every 1-2 years.  This is necessary to help insure water quality.

R.O. Membrane - The R.O. membrane would be changed when rejection rate falls to 75%. The rejection rate should be tested every year.  The membrane can last up to 12 years depending on the water quality, hardness of the water coming into the system and the frequency of filter changes. The only way to know when it is time to change the membrane is to know when the rejection rate of TDS falls below 75%.  To do this you will need a TDS Meter (total dissolved solids tester)This allows you to compare the amount of TDS in the incoming water vs. the purified water. TDS testers are a basic tool in proper maintenance on any reverse osmosis system.