What a cartridge is and why you need to replace it

A cartridge is the part inside your faucet that controls water flow and temperature. When you turn the handle, you are moving the cartridge, not opening a valve directly. Over time—usually five to ten years—the cartridge wears out. Water starts leaking from the spout even when the handle is off, or the handle becomes stiff and hard to move. Replacing the cartridge fixes both problems and costs far less than replacing the entire faucet.

The cartridge sits inside the faucet body, hidden under the handle. You cannot see it without taking the faucet apart, but you do not need special tools or plumbing experience to swap it out. The job takes 15 to 30 minutes and requires only a screwdriver, an adjustable wrench, and the correct replacement cartridge for your faucet brand.

Key Takeaways

  • Turn off the water supply under the sink before you start, and turn on the faucet to release any remaining pressure in the lines.
  • Remove the handle by unscrewing the set screw (usually hidden under a decorative cap), then unscrew the collar nut that holds the cartridge in place.
  • Pull the cartridge straight out, take it to a hardware store or look up your faucet brand online to find the exact replacement part number.
  • Insert the new cartridge with the flat edge or notch aligned the same way the old one was, then reassemble the collar nut, handle, and cap in reverse order.
  • Turn the water back on slowly and test for leaks at the base of the faucet before you consider the job complete.

Identify your faucet brand and cartridge type

The cartridge you need depends on your faucet brand. Moen, Delta, Kohler, and Pfister each make different cartridges that are not interchangeable. Look under the sink or on the faucet body for a brand name or logo. If you cannot find one, take a photo of the faucet and bring it to a hardware store, or search online for "kitchen faucet cartridge" plus the shape and color of your handle.

Once you know the brand, you have two ways to find the exact cartridge. The easiest is to remove the old cartridge and take it with you to the store—a staff member can match it directly. The second way is to look up your faucet model number (usually stamped on the faucet body or in your paperwork) and search the manufacturer's website for the cartridge part number. Order the cartridge online or pick it up at a hardware store before you start the job, so you are not left without water while you wait for a delivery.

Turn off the water and release pressure

Locate the shut-off valves under the sink—one for hot water and one for cold. Turn both valves clockwise until they stop. Do not force them; they should turn smoothly. If the valves are stuck or missing, you will need to shut off the main water supply to the house instead.

After the valves are closed, turn on the faucet handle and let water run for a few seconds. This releases the pressure trapped in the lines. You may hear air hiss out. Once the water stops, you are ready to open the faucet. If you skip this step, water will spray when you remove the cartridge.

Remove the handle and expose the cartridge

Look for a small cap or button on top of or behind the handle. This cap usually covers a set screw. Pry it off gently with a flathead screwdriver or your fingernail. Once the cap is off, you will see a screw. Turn it counterclockwise with a screwdriver until it comes out completely. The handle should now slide off.

Underneath the handle, you will see a large nut (the collar nut) holding the cartridge in place. Use an adjustable wrench to turn this nut counterclockwise. It may be tight, so grip the wrench firmly and turn slowly. Once the nut is loose enough to turn by hand, unscrew it the rest of the way and set it aside. The cartridge is now exposed and ready to be pulled out.

Pull out the old cartridge and prepare the new one

Grasp the cartridge stem (the part sticking up) with your fingers or a pair of pliers and pull straight up. It should come out with steady pressure; do not twist or rock it side to side. If it is stuck, try wrapping a rubber band around the stem for better grip, or spray a small amount of penetrating oil around the base and wait five minutes before trying again.

Once the old cartridge is out, look at the flat edge or notch on the side of the stem. This alignment mark shows you which direction the cartridge was installed. Before you insert the new cartridge, make sure it is oriented the same way. Most cartridges have a small flat spot or a notch that must line up with a matching groove inside the faucet body. If you install it backward, the hot and cold will be reversed, or the handle will not move smoothly.

Install the new cartridge and reassemble

Insert the new cartridge straight down into the faucet body, with the flat edge or notch aligned the same way the old one was. Push it down firmly until it sits flush. You should feel slight resistance, but it should not require force. If it does not slide in smoothly, pull it out and check the alignment again.

Once the cartridge is seated, screw the collar nut back on by hand first, then tighten it with the adjustable wrench. Turn it clockwise until it is snug—firm enough that it will not loosen, but not so tight that you strip the threads. Slide the handle back onto the stem and insert the set screw. Tighten the screw with a screwdriver, then snap the decorative cap back on.

Turn the water back on and check for leaks

Turn both shut-off valves under the sink counterclockwise slowly. Open them all the way. Turn on the faucet and let water run for 10 to 15 seconds to flush out any debris from the lines. The water may sputter or come out cloudy at first—this is normal and will clear in a few seconds.

Once the water runs clear, test the handle in both directions and check the temperature. The hot and cold should work correctly. Look under the sink and around the base of the faucet for any drips. If you see water pooling, turn off the valves and tighten the collar nut a quarter turn more. If the leak continues, the cartridge may be installed backward—remove it, flip it 180 degrees, and reinstall it. If the handle is stiff or the water still leaks from the spout, the new cartridge may be defective; return it and try a replacement.

Frequently Asked Questions

What if the cartridge is stuck and will not come out?

Spray penetrating oil (like WD-40) around the base of the cartridge where it meets the faucet body. Let it soak for 5 to 10 minutes, then try pulling again. If it is still stuck, wrap a rubber band around the stem for grip, or use a cartridge puller tool (available at hardware stores for $10 to $20). Do not twist or rock the cartridge side to side, as this can damage the faucet body.

Can I replace the cartridge without turning off the water?

No. If you do not shut off the water first, it will spray out when you remove the cartridge, and you will not be able to see what you are doing. Always close the shut-off valves under the sink and release pressure by running the faucet before you start.

How do I know which way the cartridge should face?

Look at the old cartridge before you remove it. Most cartridges have a flat edge or a small notch on the stem. The new cartridge must be installed with this mark facing the same direction. If you are unsure, check the packaging or the manufacturer's website for a diagram showing the correct orientation.

What if hot and cold are reversed after I install the new cartridge?

The cartridge is installed backward. Turn off the water, remove the collar nut, and pull the cartridge out. Rotate it 180 degrees and reinstall it with the flat edge or notch facing the opposite direction. Reassemble and test again.

How long does a new cartridge usually last?

A quality replacement cartridge typically lasts five to ten years, depending on water hardness and how often the faucet is used. Hard water and frequent use shorten the lifespan. If your cartridge fails much sooner, the problem may be sediment in the water lines—run the faucet for a minute to flush debris before you assume the cartridge is defective.