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Reverse Osmosis Replacement Filters

Reverse Osmosis systems generally include 2-3 filters and a membrane that must be replaced periodically. The different filters represent the different stages that the water goes through while being purified.

Reverse Osmosis Stages

Stage 1 - Pre-Membrane

Before entering the RO membrane - water must be filtered to remove sediment and chlorine. Most water from municipal sources contains chlorine, which can damage/foul the RO membrane. Carbon is used to remove the chlorine before it reaches the membrane. There may be one or mutiple pre-filter cartridges. The first cartridge is usually a sediment cartridge followed by one or more carbon block cartridges. Simplier systems my have a combination sediment/carbon block cartridge.

Stage 2 - RO Membrane

Water is forced through the semi-permeable membrane. Impurities (reject water) that don't pass through the membrane go down the drain. Purified water (permeate) passes through the mebrane and moves to stage 3 tank and stage 4 filter(s).

Stage 3 - Storage Tank

After passing throught the membrane - water passes to a pressurized storage tank where it collects until there is a demand for water

Stage 4 - Post-Membrane

When there is demand - water leaves the storage tank and passes through one or multiple post filters - usually filled with carbon, which give the water a final "polish" before drinking.

Generally - Pre-Filters and Post-Filters in RO systems can last aroumd 6 months between changes. RO membranes can last as long as 2 years!