Reverse Osmosis Membrane: When the Reduction Falls Off

By SubcontractorHub Editorial Team·Published November 2026

People search for a reverse osmosis membrane when the drinking water slows down or starts to taste like the tap again. The useful test is a number, not a guess about the year. This page quotes one manufacturer support note. It does not rank membranes, and it does not tell you which housing to buy.

What the Reverse Osmosis Membrane Note Actually Says

GE Appliances' support note on when to change the membrane, fetched the day this was written, says the prefilter and the postfilter are typically changed every six months. It says the reverse osmosis cartridge usually lasts 3 to 5 years. Those are two different parts. Changing the filters on schedule is the short visit. The membrane is the longer one, and the note does not tell you to swap it every time you swap a carbon block.

The test the note prints is total dissolved solids reduction. When reduction falls below 75 percent, replace the reverse osmosis cartridge in addition to the prefilter and the postfilter. TDS should be checked annually. The replacement rule is that 75 percent line, or a maximum of every 3 to 5 years, as needed. "As needed" and "maximum" are both in the sentence. A membrane that still reduces TDS is not automatically due because a calendar page turned, and a membrane that has fallen below 75 percent is not saved by being newer than three years.

The note says a water test kit can come from an independent laboratory, and that the owner's manual for the model you own is where the kit is described. It also says GE does not recommend another manufacturer's membrane or filters. This article repeats that as GE's instruction for GE systems. It is not a rule this page invents for every brand under a sink.

How to Read a Reverse Osmosis Membrane Test

Reduction is a comparison, not a single meter number. You need the TDS of the water going in and the TDS of the water the membrane made. The note does not print the arithmetic. If the treated water is no longer far below the tap, that is the moment to do the test instead of guessing from taste. Taste is why the customer called. The 75 percent line is why you change the cartridge.

A slow stream can be a clogged prefilter, a tank that is not holding pressure, or a membrane. The GE note does not give a flow rate that means "membrane." It ties the membrane decision to TDS reduction and to the 3 to 5 year maximum. Change the six-month filters, then retest, before you tell the customer the membrane is the part that failed. If you skip that, you will sell a cartridge the note did not ask for.

What This Page Will Not Add to a Reverse Osmosis Membrane

Other pages in a public search printed rejection bands, chlorine rules, and prices. They were not the note fetched for this article, so their numbers are not used. No chlorine concentration, no "percent rejection means healthy," and no dollar figure for a cartridge appears here. A cost model that already lives on this site is the reverse osmosis system cost calculator. Its prices are that tool's. They are not repeated, and they are not confirmed by the GE note.

Sediment ahead of the membrane is a different visit. When a cartridge housing is due, and what one Pentair manual says about months and pressure, is sediment filter replacement. Sizing the micron and the flow, which is not a replacement date, is the sediment filter sizing calculator. Carbon after sediment is the carbon filter sizing calculator.

A softener and a membrane answer different complaints. Hardness in the heater and the shower is not what a single drinking-water membrane fixes. The difference is water softener versus reverse osmosis. This page does not retell that comparison. It only says when the GE note says the membrane itself is due.

How a Dealer Should Write the Visit

The service file should show the test, not a slogan. A customer who hears "it has been a few years" cannot see the 75 percent line. Write the two TDS readings, the date, and whether the prefilter and postfilter were changed on that visit.

1. Confirm the system is the one the note applies to. GE's line is GE's line.
2. Read TDS on the feed and on the treated water. The note says check annually.
3. If reduction is below 75 percent, the note says replace the membrane and the filters.
4. If the membrane is at the 3 to 5 year maximum, the note says replace as needed even without waiting for a worse test.
5. Prefilter and postfilter stay on the six-month habit the note calls typical.
6. Do not copy another brand's membrane into a GE housing. The note says not to.

None of that is a plumbing code section. It is one support article. If the owner's manual for the model disagrees, the manual wins. The phone number printed on the GE page is 1-800-952-5039, option 1, weekdays. This article is not that help line.

What a Public Search Showed, and What Was Left Out

A public search on November 9, 2026 for when to replace a reverse osmosis membrane returned the GE note, dealer blogs, and an industrial water-treatment article. Ahrefs volumes were not refreshed. Demand here is that public result list only. No monthly search count is invented.

Dealer pages that ranked rejection in bands, or that named a two-to-four-year life without being the GE note, were not fetched as the source of a number. Using them would have stacked a second interval on top of 3 to 5 years. One source is enough. If you service a brand that is not GE, read that brand's manual before you quote 75 percent as if it were universal.

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