The Rainsoft 9338 Reverse Osmosis System can be found here:
http://www.waterfilters.net/Rainsoft...m_p_0-895.html
The replacement sediment filter for the first stage is the Pentek P25 water filter:
http://www.waterfilters.net/Pentek/w...ilters/P25.htm
The replacement sediment filter for the second stage is the Pentek P5 water filter:
http://www.waterfilters.net/Pentek/w...ilters/P25.htm
The replacement reverse osmosis membrane for the third stage is the GE Desal CTA-16 replacement membrane:
http://www.waterfilters.net/Desal-GE...e_p_0-868.html
The replacement post GAC Inline Water Filter for the fourth stage is the Omnipure CL6ROT33-B replacement filter:
http://www.waterfilters.net/Omnipure...r_p_0-754.html
As always, the replacement time depends on the water quality. For best results it is recommended that you change the first two stages every 3 to 6 months, the membrane every 1 to 3 years and the post filter every time the membrane is replaced. If you replace the first two sediment filters often it will help extend the life of the reverse osmosis membrane, which is a more expensive filter.