How Do I Replace a Faucet Cartridge?

Quick Answer

Shut off the water at the angle stops under the sink, pop off the handle cap, unscrew the handle, remove the brass retaining nut or clip, pull the old cartridge straight out, slide the matching new cartridge in, and reassemble in reverse order.

Total time: 30 to 60 minutes for a first time DIYer. Cost: typically 10 to 40 dollars for a brand matched cartridge, versus 150 to 400 dollars for a plumber call out.

The single most important step is bringing the old cartridge to the hardware store. Cartridges look similar but are model specific, and the wrong one will not seal.

Plumbing disclaimer: if you smell gas, see water damage in the wall, or your shutoff valves do not close, stop and call a licensed plumber. This guide covers basic faucet repair only.

Why faucets drip

Inside every single handle faucet is a cartridge: a cylindrical insert with rubber O rings and a ceramic disc that controls flow and temperature. Hard water, mineral deposits, and routine wear eventually crack the O rings or score the ceramic. Once that happens, water leaks past the seal and drips from the spout even when the handle is off.

Drips waste roughly 3,000 gallons per year and stain the basin. Cartridge replacement is the standard fix on Moen, Delta, Kohler, Pfister, and most other single handle brands.

Tools and parts checklist

• Allen wrench set (often included with the new cartridge).
• Adjustable wrench or channel lock pliers.
• Flathead screwdriver.
• Needle nose pliers.
• Plumber s silicone grease (small tube, 5 to 8 dollars).
• Old towel and a small bowl for screws.
• Replacement cartridge (Moen 1225 for two handle Moen lavatory faucets, Moen 1222 for single handle Posi Temp showers, Delta RP19804 for single handle kitchen faucets, etc. Always confirm against your faucet model number).

Step 1: Shut off the water

1. Look under the sink for two angle stop valves (hot and cold).
2. Turn each clockwise until snug. If the valves are seized, shut off the main supply at the meter or main shutoff valve.
3. Open the faucet to drain residual pressure.
4. Plug the drain with a rag to prevent dropped screws from disappearing.

Step 2: Remove the handle

1. Pry off the small decorative cap on top or front of the handle with a flathead.
2. Use an Allen wrench to loosen the set screw (do not fully remove it; just loosen enough to lift the handle).
3. Lift the handle straight up and off.

Step 3: Remove the trim and retaining hardware

1. Some faucets have a decorative chrome dome under the handle. Unscrew it by hand or with channel lock pliers wrapped in tape to avoid scratches.
2. Locate the retaining nut or U shaped retaining clip that holds the cartridge in place.
3. For a nut, use an adjustable wrench to turn counter clockwise.
4. For a clip, pull it straight up with needle nose pliers.

Step 4: Pull out the old cartridge

1. Grip the cartridge stem with pliers and pull straight up. Wiggle gently if it sticks.
2. If the cartridge is stuck, use the cartridge puller tool that came with your new cartridge (Moen sells one for around 12 dollars). Thread it onto the cartridge stem and lever it out.
3. Inspect the cartridge cavity for mineral buildup. Wipe clean with a vinegar soaked cloth.

Step 5: Install the new cartridge

1. Compare the old and new cartridges side by side. The O rings, splines, and stem length must match exactly.
2. Apply a light coat of plumber s silicone grease to all O rings on the new cartridge.
3. Align the new cartridge in the correct orientation (most have a notch or arrow that must face forward or up; check the included instructions).
4. Push it straight down into the cavity until it seats fully.

Step 6: Reassemble in reverse

1. Reinstall the retaining clip or nut. Snug the nut hand tight, then a quarter turn with the wrench. Do not over tighten.
2. Replace the decorative dome.
3. Slide the handle on and tighten the set screw.
4. Snap the cap back into place.

Step 7: Test for leaks

1. Turn the angle stops back on slowly. Listen for hissing or watch for drips at the connections.
2. Open the faucet partly to flush any debris, then close it.
3. Run hot and cold separately for 30 seconds each, then leave the faucet off and check the spout after five minutes for any drip.
4. Check under the sink with a paper towel for any moisture at the supply lines.

Troubleshooting

• Faucet drips after replacement: the cartridge is misaligned. Remove the handle and rotate the cartridge 180 degrees.
• Hot and cold are reversed: common after replacement. Pull the handle, lift the cartridge slightly, rotate it 180 degrees, and reinsert.
• Weak flow: debris likely settled in the aerator. Unscrew the spout tip and rinse the screen.
• Leak under the sink: the supply line nut may have loosened during the work. Snug both lines a quarter turn with the wrench.

FAQs

How do I find my faucet model number?

Check under the sink on the faucet body, on the original receipt or installation paperwork, or by photographing the faucet and using the manufacturer s online tool (Moen and Delta both have free model finders).

Should I replace the O rings instead of the whole cartridge?

If the ceramic disc is still smooth and only the O rings are worn, you can buy an O ring kit and replace them in place. For a faucet older than 8 to 10 years, the full cartridge is usually the better call.

Why does my faucet still drip after a new cartridge?

The most common cause is debris in the cartridge cavity. Flush thoroughly with water before reinstalling. The second most common cause is buying the wrong cartridge model.

Do I need to turn off the main water supply?

No, as long as the under sink shutoffs work. Only use the main if the local valves are seized or leaking.

The takeaway

Cartridge replacement is one of the highest payoff plumbing repairs a homeowner can do. Match the cartridge exactly, grease the O rings, do not over tighten the retaining nut, and your faucet will run quietly for another decade.