CFS 50 GPD RO MEMBRANE — STANDARD 1812 ELEMENT A direct replacement for TW30-1812-50 and the other 50 GPD 1812 elements, in the standard size used across residential four and five stage reverse osmosis systems. WHAT THE MEMBRANE ACTUALLY DOES This is the stage that strips dissolved solids. The prefilters ahead of it handle particles and chlorine; the membrane is what takes total dissolved solids down. It is also the expensive part of the system, which is why the carbon stage in front of it matters so much — chlorine reaching a thin film composite membrane is the single thing that shortens its life fastest. If your carbon is overdue, change it with the membrane. MATCH THE RESTRICTOR TO THE RATING A membrane only produces against back pressure, and that pressure comes from the drain line flow restrictor rather than from the membrane itself. A 50 GPD element wants roughly a 500 ml restrictor. Put it behind a restrictor sized for a different rating and you get slow production, a drain that runs constantly, or no water at all. Replacing the restrictor at the same time saves the troubleshooting. WHAT IT REPLACES TW30-1812-50 and TW30-1812-50HR, W-1812-50, TFM-50, TLC-50-M, TE-1812, TW-1812-50D, RE1812-50, 560018, 80722 and 92035. The element measures 11.75 by 1.75 inches and seals in the nominal 2 inch inside diameter vessels these systems use. If the membrane you are pulling out is a 50 GPD 1812, this one drops into the same housing. WHEN TO CHANGE IT About once a year on typical municipal water, longer on soft water and shorter on hard. Let the system fill and drain once before you drink from it. A rising TDS reading at the tap is the usual sign the membrane is done. Compatible replacement membrane. Part numbers are for reference only.