How to Replace a Faucet Cartridge
The general procedure for replacing a faucet cartridge or stem on any single-handle or two-handle faucet: getting the handle off, what holds the cartridge in, putting the new one in the right way round, and what to check before you order.
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Short answer. Shut off both supply valves and drain the faucet. Take the handle off, remove whatever holds the cartridge in (a nut, a clip, or a bonnet), and pull it straight out. Photograph it in place first. Match the replacement on type, splines, length, diameter and rotation, line it up the same way the old one sat, and reassemble. Single-handle ball faucets have no cartridge; they take seats and springs.
Before anything comes apart
- Shut off both supply valves under the sink and open the faucet to drain the line.
- Close or cover the drain. Set screws, clips and index caps are small and go straight down.
- Lay a towel in the sink so a dropped handle does not chip it.
- Photograph the faucet and, once the handle is off, the cartridge in place. That photo is what tells you how the new one goes in.
Step 1: get the handle off
Look for the screw. It is usually in one of three places:
- Under a decorative cap on top of the handle, often marked hot and cold. Pry it off with a thin blade or a fingernail.
- A small set screw on the side, back or underside of the handle. Most take a 3/32 or 1/8 inch hex key.
- No screw at all. Some newer handles pull straight off, and some unscrew at a skirt around the base. See how to remove a faucet handle with no visible screw.
Step 2: release the cartridge
Under the handle you will find what holds the cartridge in the faucet body:
- A retaining nut or bonnet that unscrews counterclockwise. Hold the faucet body steady so you do not twist the whole faucet on the deck.
- A U-shaped clip that slides out sideways. Pull it with needle-nose pliers.
- A threaded stem on a two-handle faucet, which unscrews from the body as one piece.
On some faucets there is a dome cover or a trim sleeve to remove first.
Step 3: pull it out square
Pull the cartridge straight up, by the stem, with pliers if needed. A slight back and forth twist helps break it free. Pulling at an angle makes it bind. If it will not move, stop before something breaks and read stuck cartridge will not come out.
Once it is out, look into the faucet body. Clean out grit and scale with a rag, and on two-handle faucets check the seat at the bottom of the bore for pitting.
What you are holding
| What came out | What it is | What usually goes with it |
|---|---|---|
| A plastic or brass cylinder with a stem, from a single-handle faucet | Single-lever cartridge | Nothing else in most cases |
| A short brass or plastic unit that turned about a quarter turn | Ceramic disc unit | Possibly seats and springs underneath; a matching unit for the other side |
| A long brass stem with a rubber washer and screw on the bottom | Compression stem | A new washer and screw, and a seat if the old one is pitted |
| A cap, a cam and a ball with holes, from a single-handle faucet | Ball valve, not a cartridge | Seats and springs, sometimes a new ball and cam |
Step 4: match the replacement
A part that looks right is not enough. Match it on:
- Type of valve, from the table above.
- The stem tip: spline count, or its shape if it is not splined.
- Overall length, measured out of the faucet against a tape.
- Diameter, especially on single-lever cartridges, where look-alikes differ by a few millimeters.
- Which way it turns off. On two-handle faucets the hot and cold units are often mirror images.
- Anything between the handle and the cartridge, like an extension or adapter, that has to be reused.
If you know the part, browse replacement cartridges or stems. If you do not, send a photo of the part next to the handle and a specialist confirms the match. The CID Finder works it down from length and spline count if you would rather measure.
Step 5: install and test
- Lightly grease the O-rings with silicone faucet grease if the new cartridge is dry.
- Line it up the way the old one sat. Kohler’s service instructions for one of its valves note the cartridge only fits one way; others fit two ways and reverse hot and cold if they go in wrong.
- Seat it fully by hand before the nut or clip goes back on. It should sit as deep as the old one did.
- Snug the nut without cranking it.
- Refit the handle in the off position.
- Open the supply valves slowly and check for leaks at the handle and spout, and that hot is on the hot side.
When to call a plumber
Bring in a pro if the cartridge is seized or the stem has broken off in the body, if the faucet body is cracked, or if the supply valves will not close. Plumbers send us the photo on those jobs too.
Common questions
Do I need to turn off the water to replace a faucet cartridge?
Yes. Close both supply valves under the sink, then open the faucet to drain the line and relieve pressure. If the valves will not close fully, shut off the main. A cartridge pulled under pressure will spray.
Can a new cartridge go in backwards?
Many can. Single-handle cartridges installed 180 degrees out swap hot and cold, and some only seat one way on their tabs or pins. Photograph the old one in place before you pull it, and line up the new one the same way.
Should I grease the new cartridge?
Only with silicone grease made for faucets, and only on the O-rings and outside seals. Petroleum grease and sprays damage the rubber. Many new cartridges come pre-lubricated.
My faucet has one handle but no cartridge under it. What is it?
Probably a ball valve: a cap, a cam, and a ball with holes in it. Ball valves have no cartridge. A drip on one is fixed with new rubber seats and springs, not a cartridge.
How do I know which cartridge to buy?
Match it on more than looks: the type of valve, the spline count on the stem, the overall length, the diameter, which way it turns off, and which side it came from. If the faucet has no readable brand or model number, a photo identification is the safer route.