How to Replace a Leaking Bathroom Faucet Cartridge

Water is relentless when it finds a path through a worn-out seal. A dripping bathroom faucet is more than just an annoying sound; it is a steady drain on your water bill and a slow erosion of your plumbing fixtures. When your handle no longer stops the flow regardless of how hard you crank it, the internal cartridge has likely reached the end of its lifespan. Replacing this component is the definitive fix for most modern single-handle or dual-handle faucets. You do not need a plumber to handle this, provided you follow the sequence of pressure relief and delicate handling. When done well, your faucet will operate with a smooth, firm action, and the drip will vanish immediately.

1. Kill the Water Supply. Locate the shut-off valves under the sink and turn them clockwise until they stop. Open the faucet handle to drain any remaining pressure in the lines.
2. Free the Handle First. Identify the set screw, usually hidden under a small cap or located on the side of the handle. Loosen it with an Allen wrench or screwdriver and pull the handle straight off.
3. Uncover the Cartridge. Unscrew the decorative bonnet or collar covering the valve body. Use an adjustable wrench for this, but wrap a rag around the chrome first to prevent scratching the finish.
4. Pull Out the Old Part. Most cartridges are held in by a brass retaining nut or a U-shaped clip. Remove the clip with needle-nose pliers or unscrew the nut, then pull the cartridge out firmly.
5. Seat the New Cartridge. Clean any debris or mineral deposits from the inside of the valve body using a soft brush. Align the tabs on the new cartridge with the slots in the housing and push it until it is fully seated.
6. Test for Leaks. Replace the retaining clip or nut, screw the bonnet back on, and reattach the handle. Slowly open the water valves and check for leaks while cycling the faucet handle.