It is very important to determine the style of reverse osmosis membrane your system uses. It will either be a CTA membrane or a TFC style membrane. CTA membranes are made to allow contact with chlorine in the water. TFC membranes are chlorine "intolerant" and cannot come into contact with chlorine. The chlorine will destroy a TFC membrane. Therefore TFC systems are ALWAYS equipped with a carbon pre-filter that removes the chlorine. TFC can be utilized on ANY tap water system, well or city. CTA or Cellulose Tri-Acetate membrane is an organic membrane. CTA membranes typically use a sediment prefilter and pass the chlorinated water into the tank. The carbon post filter then removes the chlorine. TFC or Thin Film Composite membrane is a synthetic membrane that has a removal percentage between 94-99%. A TFC membrane uses a carbon pre filter before the membrane to remove the chlorine and then another carbon filter after the membrane to "polish" the water just before dispensing. TFC membranes have a higher rejection rate of many chemicals than CTA membranes and the extra carbon filter additionally removes more contaminants than the single carbon filter used in CTA systems. TFC membranes will typically last 3 to 5 years. CTA membranes typically last 18 to 24 months. CTA has a typical removal percentage of 86-94%. Since the CTA is an organic membrane, it needs chlorine to protect itself from damaging molds and bacteria. The CTA membrane MUST be run with chlorinated water and cannot be run on non-chlorinated water systems (wells). The only way to know if your membrane is working correctly is to measure and compare the TDS (total dissolved solids) in the incoming feed water and the product drinking water.