Rainsoft 21179 Three Stage RO System


The Rainsoft 21179 features a 1 micron carbon block prefilter, a 50 GPD TFC membrane, and another 1 micron carbon block for the post filter. The Rainsoft 21179 uses a carbon block pre-filter to reduce sediment, chlorine, and chlorine by-products before the membrane filters out impurities larger than .001 microns. The carbon block post filter treats for taste and odor. These filters are high-quality aftermarket RO filters that will produce outstanding drinking water.


Note: If your Rainsoft reverse osmosis system is from 2013 or newer, it most likely is the Ultrefiner II. The Ultrefiner II requires proprietary filters that must be purchased from a Rainsoft dealer. Conversion kits to generic non-OEM replacement filters are available.



  • STAGE 1 – Carbon Block Pre-Filter (OMB934-5M - Rainsoft Part#: 9557 or 18557) – Replace Every 12 Months
  • STAGE 2 – RO Membrane TFC 50 GPD (TFC-RS9-50 - Rainsoft Part#: 9568, 18644, 18571, 12447, 21179, or 21176) – Replace Every 24 Months
  • STAGE 3 – Carbon Block Post Filter (OMB934-1M) – Replace Every 12 Months