CTA (cellulose triacetate) membranes used to be significantly less expensive than TFC (Thin Film Composite) membranes, but not any more. A CTA membrane is considered to be inferior to a TFC membrane because it does not last as long (only 18-30 months) and produces water which is less pure than that produced by a TFC membrane.

Under some circumstances, you can replace your CTA membrane with a TFC membrane:

- If you have non-chlorinated water: you can always replace the CTA membrane with a TFC membrane;

- If you have chlorinated water: you must have a carbon pre-filter to remove the chlorine which will otherwise ruin the membrane:
         - If your R.O. system runs the water through a carbon filter before going to the membrane, then you can replace the CTA membrane with a TFC membrane.
         - If your R.O. system only runs the water through a sediment filter before going to the membrane, you can modify your system in one of two ways:
                 - insert a carbon filter into the sediment filter housing (so that water flows through the carbon filter before going to the membrane). In order to minimize clogging of the carbon filter, we recommend the Plekx filter which we sell for $10 plus postage. It is good for 2500 gallons of chlorinated water, so if you use 7 gallons per day (including waste), it will last for almost a year. OR
                 - add a new housing in front of your sediment filter housing. Then put the sediment filter in the new housing and the carbon filter into what used to be your sediment filter housing. We will sell you a new housing with fittings and tubing for $13 plus postage. The carbon filter we recommend in this configuration is the Matrikx +1 which we sell for $15.

In some situations, people want to leave chlorine in the water. In this case, you can't have a carbon filter and must use a CTA membrane. We sell three types of CTA membranes (all of these are interchangeable):

         - the Plymouth Products (fka Ametek) ROM 16C (16 gpd) membrane (part number 155415) for $64.65
         - the DESAL CTA-16 (16 gpd) membrane for $40.00
         - the Osmotik (14 gpd) CTA membrane for $40.00

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