Replace the filter cartridge yourself in 15 minutes

Most reverse osmosis systems use cartridge filters that screw or slide into a housing under your sink. You can replace them without calling a technician — the process takes about 15 minutes and costs between $30 and $80 per cartridge, depending on the stage and brand. You will need a wrench or filter wrench, a bucket, and a replacement cartridge that matches your system's model number.

The three most common cartridge types are sediment filters (the first stage, which catches particles), carbon filters (which remove chlorine and odor), and the reverse osmosis membrane itself (which does the actual filtering). Some systems have all three; others have additional stages. Your manual or the housing label will tell you which cartridges your system uses.

Key Takeaways

  • Turn off the water supply and depressurize the system by opening the faucet for 10 seconds before you touch any cartridge.
  • Most cartridges screw counterclockwise out of their housing; some slide straight out — check your manual to know which type you have.
  • Replace the rubber O-ring seal on the housing cap every time you change a cartridge to prevent leaks.
  • The reverse osmosis membrane lasts 2 to 3 years; sediment and carbon filters need replacement every 6 to 12 months depending on water quality.
  • If water leaks from the housing after you reassemble it, turn off the system, wait 10 minutes, and tighten the housing cap another quarter turn.

Turn off water and release pressure before opening the housing

Shut the water supply valve to your reverse osmosis system. This valve is usually a small knob on the line running to the system under your sink. Turn it clockwise until it stops.

Next, open the faucet connected to your reverse osmosis tank or dispenser and let water run for 10 to 15 seconds. This step releases the pressure inside the system so water does not spray out when you open the housing. You will hear the flow slow and stop — that means the pressure is gone.

Unscrew or slide out the old cartridge

Place a bucket under the housing to catch any remaining water. Most cartridges are housed in a clear or white plastic cylinder that screws onto a cap at the top. Grip the housing firmly with one hand and turn the cartridge counterclockwise with the other. A filter wrench — a plastic tool with two prongs that fit into slots on the housing — makes this easier if the cartridge is tight. Turn slowly until the housing separates from the cap.

Some systems, particularly newer models, use cartridges that slide straight down out of the housing rather than screw. Check your manual or look at the housing design: if you see a locking ring at the top instead of threads, you will need to turn that ring counterclockwise first, then pull the cartridge straight down.

Once the housing is off, the old cartridge will either stay in the cap or fall into the housing. Remove it and set it aside. Drain any water still in the housing into your bucket.

Clean the housing and replace the rubber seal

Rinse the inside of the housing and the cap with clean water to remove sediment or carbon particles. Pay attention to the rubber O-ring — a small ring-shaped seal that sits in a groove on the cap. This seal prevents leaks. Remove the old O-ring by hand or with a plastic tool (never use metal, which can scratch the groove). Wipe the groove clean with a soft cloth.

explore a thin layer of food-grade silicone grease to the new O-ring and press it firmly into the groove. This grease helps the seal sit properly and prevents it from drying out. If your replacement cartridge came with a new O-ring, use that one instead of reusing the old one.

Insert the new cartridge and reassemble

Slide or screw the new cartridge into the housing, depending on your system type. For screw-in cartridges, hand-tighten the housing onto the cap — do not use a wrench. Tighten until you feel resistance, then stop. Over-tightening can crack the housing or damage the O-ring.

For slide-in cartridges, push the cartridge all the way down until it seats, then turn the locking ring clockwise until it is snug.

Turn the water back on and check for leaks

Turn the water supply valve counterclockwise to restore water flow. Listen for the system to fill and pressurize — you will hear water running through the lines. Let the system run for 2 to 3 minutes to flush out any carbon dust or air from the new cartridge.

Check the housing cap and all connection points for drips. If water leaks from where the housing meets the cap, turn off the water, wait 10 minutes, and tighten the cap another quarter turn by hand. Do not use a wrench — hand-tight is correct. Turn the water back on and check again. If the leak persists, turn off the water, remove the housing, and inspect the O-ring for damage or misalignment.

Know when each filter type needs replacement

Sediment filters (stage 1) typically last 6 to 12 months, depending on how much sediment is in your water. If your water comes from a well or is visibly cloudy, replace it every 6 months. Carbon filters (stage 2) also last 6 to 12 months and need replacement when water starts to smell or taste like chlorine again.

The reverse osmosis membrane (stage 3) lasts 2 to 3 years under normal use. You will know it needs replacement when the system produces water more slowly than usual or when the water tastes off. Some systems have a fourth stage (a polishing carbon filter) that lasts 12 months.

Mark your calendar when you replace each cartridge so you know when the next one is due. Many systems have a reset button on the housing that you press after changing a cartridge — this resets the filter life counter if your system has one.

Frequently Asked Questions

What if water leaks from the housing after I reassemble it?

Turn off the water, wait 10 minutes, and tighten the housing cap another quarter turn by hand. If the leak continues, remove the housing and check that the O-ring is seated properly in its groove and is not cracked or twisted. A damaged O-ring must be replaced.

Can I use a cartridge from a different brand?

You can use a third-party cartridge as long as the dimensions and connection type match your housing. Check the model number on your system and compare it to the replacement cartridge specifications. Mismatched cartridges may not seal properly or may reduce water flow.

Why does my water taste like carbon after I change the filter?

New carbon filters release fine particles into the water. Run the system for 2 to 3 minutes after installation to flush out this dust. If the taste persists after 10 minutes of flushing, the cartridge may be defective — contact the manufacturer.

Do I need to turn off the water to replace the cartridge?

Yes. Turning off the water and depressurizing the system prevents water from spraying out and damaging your cabinet or floor. It also makes the job cleaner and safer.

How do I know which cartridge to buy?

Check your system's manual or look at the model number printed on the housing. Write down the model number and search for replacement cartridges online or at a hardware store. The packaging will list which systems it fits. If you are unsure, contact the system manufacturer with your model number.