What is a faucet cartridge?
Updated August 2026
A faucet cartridge is the removable valve body inside a faucet that meters how much water passes and, on a single-handle mixer, how much of it is hot. Moving the handle rotates or slides a ceramic disc, a brass sleeve, or a plastic stem against matching ports, while rubber seals hold back pressure at every position in between. It is the only part of a faucet that wears out from ordinary use, which is why swapping one usually restores the fixture to new behavior.
Where it is
The cartridge hides under the handle, and reaching it follows the same four moves on nearly every brand. Close both stop valves under the sink, pry off the decorative cap or button, back out the hex or Phillips screw beneath it, lift the handle away, then remove whatever pins the cartridge down: a horizontal brass pin, a threaded retaining nut, or a U-shaped clip. Pull it straight up and note its orientation, because reinstalling one 180 degrees off swaps hot and cold. Cartridges are brand-specific and often model-specific, so photograph the old part and any markings under the faucet, or carry the part to the counter.
What it does
Every drip from a closed faucet traces to a seal that no longer meets its seat. Grit scores the ceramic discs, O-rings harden and take a set, and scale builds wherever water sits still. Symptoms arrive in sequence: a handle that turns stiff or gritty, a temperature setting that drifts hot after a minute, a faint drip at the spout, then a drip you can hear from the next room. A leak of one drop per second wastes roughly 3,000 gallons a year, and the same worn seal eventually weeps down the shaft into the cabinet. Water pressure sets the pace. Above 80 psi, cartridges that should give 10 years are finished in 3 to 5.
Maintenance
Cartridges get replaced on symptom rather than on a calendar, but two habits stretch their life. Hold house pressure between 50 and 60 psi, and keep grit from reaching the valve by rinsing the aerator every 6 to 12 months (aerator cleaning). When the swap comes, buy the exact brand part, coat the new O-rings with silicone plumber's grease instead of petroleum jelly, and flush the open lines into a bucket for 5 seconds before seating the new cartridge. Two or three cartridges in five years says the faucet body or the water quality is the real culprit: see how long faucets last and the faucet checklist, with the cost of ignoring a dripping faucet for what waiting adds up to.
What it costs to replace
A replacement faucet cartridge runs $10–40 for the cartridge, or $150–250 with a plumber, against $250–600 for a new faucet.
OnOtto's photo scan identifies parts like this in your home and builds the maintenance schedule for you. See how the scan works.
Frequently asked questions
How do I find the right replacement cartridge?
Take the old one with you, or photograph it beside a ruler. Brand comes first: check the escutcheon, the handle screw cover, or stamps on the underside of the faucet body. Then match the model, because Moen alone sells a dozen incompatible designs. Hardware stores stock the common Moen, Delta, and Kohler families for $10–40. Register the faucet if you still can, since Moen and Delta both ship warranty cartridges at no charge.
Should I replace the cartridge or the whole faucet?
Replace the cartridge when the body is solid brass, the finish still looks right, and this is the first or second cartridge in a decade. Replace the faucet when the base wobbles, the finish flakes, the spout leaks where it meets the deck, or the brand is gone and no part exists. A cartridge is $10–40 and an hour of your time. A mid-grade faucet is $250–600 installed, and no cartridge saves a corroded body.
I put in a new cartridge and it still drips. Why?
Two usual reasons. On Delta-style valves, the seats and springs in the bottom of the body are separate parts, and reusing worn ones lets water slip past a brand-new cartridge; that kit runs $8–15. On ceramic-disc models, a grain of sand from the supply line wedges between the discs, so shut the water off, pull the cartridge again, and flush both lines into a bucket before reinstalling.
Do I have to shut off water to the whole house?
Usually not. The two angle stops under the sink isolate that fixture, and a quarter-turn stop closes in a second. Old multi-turn stops are the catch: they seize, or the packing weeps once you disturb them. Close them slowly with a towel underneath. If a stop will not seal, use the home's main shutoff and plan on replacing that stop for $75–150 while everything is already apart.