RO filter replacement: which cartridges, when, and how

Advertised prices, verified

How to replace RO filters without a service call

1. Identify your exact system and stages. Find the model number on the housing or manifold and list the stages in order: sediment, one or two carbon blocks, membrane, post-carbon, and any remineralizer. Buying by stage position without the model number is how people end up with cartridges that do not seat.
2. Shut off feed and tank, then depressurize. Close the feed valve on the cold line and the valve on top of the storage tank, then open the RO faucet until flow stops. Working on a pressurized housing sprays the cabinet and can crack the sump threads when you fight the wrench against pressure.
3. Swap cartridges cleanly and in order. Open each housing with the supplied wrench, wipe the sump, seat the new cartridge the right way up, and check the O-ring is seated and lightly lubricated with silicone grease. The membrane slides into its own horizontal housing and needs its brine seal pushed fully home.
4. Flush before you drink. Reopen the valves, check every housing for weeping, and run the system to drain for the flush period the manufacturer prints. Fresh carbon sheds fines and a new membrane carries preservative, so the first tankfuls are for the drain, not the glass.

Which filters change and roughly when

Pre-filters do the heavy work and fail first: the sediment stage clogs and the carbon stage exhausts its ability to strip chlorine, which is what actually kills membranes. Change them on the schedule printed for your model, and sooner if flow drops or the water smells of chlorine at the RO faucet.

The membrane itself is the expensive, long-lived stage. Replace it when production slows noticeably despite fresh pre-filters or when a TDS meter shows the reading creeping toward the tap water figure. The post-carbon polisher is cheap and changes whenever taste dulls or the schedule says so.

Buying the right replacement cartridges

Standard-size systems take generic ten-inch-format cartridges from many makers, which keeps replacement costs low and is worth checking before you buy any system. Proprietary quick-change systems only accept their own maker's cartridges, so the table's replacement pricing is effectively your subscription cost.

Compatible third-party cartridges for proprietary heads exist and are cheaper, but quality varies and some vendors condition their warranty on original filters. If your system is still under warranty, stay original; after that, judge compatibles by certification marks, not by price alone. If you are still choosing a system, our best ro system for home guide weighs replacement cost alongside purchase price.

Common questions

How do I know it is time to replace my RO filters?

Slower fill at the faucet, a longer time to refill the tank, chlorine taste returning, or a rising TDS reading are the practical signals. Absent those, follow the schedule printed for your model rather than guessing.

Can I just replace the membrane and skip the pre-filters?

That is the one order of operations to avoid. Exhausted carbon lets chlorine reach the new membrane and ruins it quickly. Always fit fresh pre-filters when you fit a membrane, and ideally before.

What do RO replacement filters cost per year?

It depends on whether your system takes standard or proprietary cartridges. The table shows the current published cartridge prices from each vendor, and a typical set works out near $1,531 across the vendors we track.

Do I need to sanitize the system when changing filters?

Sanitizing the housings and tank with the manufacturer's recommended procedure once a year, usually at the pre-filter change, keeps biofilm out of the downstream stages. It adds a few minutes and is worth the habit.

Browse by system type

• Compare Water softeners on advertised prices
• Compare Salt-free softeners on advertised prices
• Compare Whole-house filters on advertised prices
• Compare Reverse osmosis systems on advertised prices
• Compare Shower filters on advertised prices
• Compare Countertop filters on advertised prices
• Compare Refrigerator filters on advertised prices
• Compare Iron filters on advertised prices