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In nine cases out of ten a dripping kitchen faucet means the valve cartridge, or the rubber seals and O-rings that surround it, have worn out. The cartridge is the moving part inside the handle, it wears through normal use over roughly 5 to 10 years, and it is a replaceable component costing 15 to 40 dollars — frequently free, because most major US brands cover cartridges under a limited lifetime warranty to the original owner. According to the EPA WaterSense program, a drip at one per second wastes about 3,000 gallons a year, so it is worth fixing promptly.
Where exactly is the water coming from?
Diagnose by location before you take anything apart. The three positions point at three different parts.
| Where it drips | When | Cause | Part |
|---|---|---|---|
| End of the spout | After shutoff | Valve not seating | Cartridge |
| Around the spout base | While running | Failed spout seal | O-ring kit |
| Under the handle | While running | Cartridge seal or loose bonnet | Cartridge or retaining nut |
| Inside the cabinet, at the shank | Constant | Loose mounting nut or bad gasket | Deck gasket |
| Inside the cabinet, at a hose | While running | Pinholed spray hose | Hose assembly |
| Inside the cabinet, at a supply | Constant | Failing supply line or stop | Braided supply line |
Anything in the bottom three rows is more urgent than a spout drip, because sustained moisture in a sink base swells particleboard cabinet floors and reaches the subfloor.
Why does the cartridge fail?
Inside a modern single-handle faucet, two polished ceramic discs slide across each other to open and close the water path. The ceramic itself is enormously hard and rarely the problem. What ages are the rubber seals that hold the discs against their seats and seal the cartridge into the faucet body: they take a compression set, lose elasticity, and eventually let a thin film of water past. Mineral scale in hard water and grit that entered the line after a water main repair both accelerate this by preventing a clean seal.
Two-handle faucets with compression valves fail differently. Those use a rubber washer pressed against a brass seat, and when the drip appears it is usually the washer, sometimes the seat, which can be resurfaced with a seat dressing tool or swapped if it is a removable type.
What does the repair involve?
- Close the angle stops under the sink and open the faucet to relieve pressure. Put a rag in the drain so nothing small disappears.
- Identify the model. The number is often stamped inside the escutcheon or on a tag under the sink. Cartridges are not universal, and this is the step people skip and then regret.
- Pull the handle. A small setscrew hides under a cap or behind the handle, usually taking a 7/64 or 3/32 hex key.
- Remove the retaining clip or bonnet nut, then withdraw the cartridge straight up. A puller tool helps on cartridges seized by scale; do not lever against the faucet body.
- Replace the cartridge and every O-ring in the kit, lubricate them with silicone plumbers grease — never petroleum jelly, which degrades rubber — and reassemble in reverse.
Budget 30 to 45 minutes the first time. The full walkthrough is in how to fix a leaky faucet, and the tools are listed in what tools do you need to replace a faucet.
When is a new faucet the better answer?
When the drip is coming from the body rather than the valve, when the finish has flaked to bare metal, when the shank is corroded into the sink deck, or when parts for the model are discontinued — which is the usual outcome with unbranded imports. Expected service life by build type is set out in how long do kitchen faucets last. If you are replacing, our best kitchen faucet roundup ranks by long-run owner satisfaction, and the swap itself is covered in how to replace a kitchen faucet.
We never buy, test or physically handle the products we rank. Recommendations come from aggregated owner reviews, star ratings, review volume and expert consensus — see how we rank.
More from this hub: DIY Plumbing · Best kitchen faucet · Fix a leaky faucet · Replace a bathroom faucet · How we rank