Why does my faucet drip when it's off?
Updated August 2026
A faucet that keeps dripping after you shut the handle almost always comes down to a worn cartridge, washer, or O-ring that can no longer seal against the valve seat. The rubber and plastic inside every faucet hardens and deforms with years of hot water and mineral contact, and once it stops sealing, pressure pushes a slow drip through. The part costs $5–25 and a match-and-swap is one of the friendlier plumbing repairs. If a fresh cartridge does not stop it, the causes below run from most to least likely.
Safety first: a faucet that drips harder than a leaky seal should on its own is often waving a flag about whole-house water pressure. Anything over 80 psi stresses every supply line, appliance valve, and washing-machine hose in the house, and a burst hose can dump hundreds of gallons an hour. If several fixtures drip or bang, test the pressure and fit a regulator before a small drip becomes a flooded floor.
Causes, most likely first
| Cause | How likely | The fix | Typical cost |
|---|---|---|---|
| Worn cartridge, washer, or O-ring | Most common | Shut the supply stops under the sink, pull the handle and cartridge, and match the exact replacement at a hardware store. | $5–25 part |
| Corroded or pitted valve seat | Common | A rough seat cuts the new washer and keeps dripping. Reface it with a seat wrench and dressing tool, or replace a seat-and-spring set. | $10–30 |
| Water pressure over 80 psi | Occasional | High static pressure forces drips past seals that would otherwise hold. Have a pressure-reducing valve set to 50–60 psi. | $250–450 installed |
| Grit or debris under the seal | Occasional | A fleck of scale or pipe grit props the seal open. Flush the valve body and clean the aerator screen while you are in there. | Free |
| Worn-out faucet body | Rare | On a faucet past 15 years, the brass bore itself is scored and no rebuild kit will seal it. Replace the whole fixture. | $100–400 |
Check these first
- Note whether the hot side, cold side, or both drip. That points you straight at which cartridge or washer to pull.
- Shut the two supply stop valves under the sink and open the faucet to relieve pressure before you take anything apart.
- Screw a $10–15 pressure gauge onto an outside hose bib. A reading above 80 psi is the real culprit, not the faucet.
- Unscrew the aerator and check for trapped grit, which can mimic a drip by holding a droplet at the spout.
- Take the old cartridge or stem with you to match it exactly, since brands are not interchangeable.
Prevent it next time
Seals last longer when they are not fighting grit and scale. Keep the aerator on a cleaning schedule so mineral debris does not migrate back into the valve, and walk the quick checks on the faucet maintenance checklist once a year. If your pressure runs high, a regulator set to 50–60 psi protects not just the faucet but the water heater, dishwasher, and every hose in the house. A drip you ignore is not free: see what a dripping faucet actually costs over a year.
When to call a pro
Call a plumber when the valve seat is too corroded to reface, when the faucet is old enough that parts are discontinued, or when you cannot find the shutoff stops and need the main valve worked. A faucet rebuild or swap runs $150–300 in labor, and installing a pressure-reducing valve on the main is $250–450. Any drip that gets worse after a repair, or a handle that will not tighten, is worth a professional look before you strip a fitting.
Most of the causes above are maintenance problems wearing a disguise. OnOtto keeps the boring prevention on schedule so the 2 a.m. version doesn't happen.
Stop chasing symptoms, free for 30 daysFrequently asked questions
How much water does a dripping faucet actually waste?
One drip per second adds up to roughly 3,000 gallons a year, and a faster drip can pass 5 gallons a day. That shows up as a few dollars a month on the water bill for a single faucet, more if it is the hot side and your water heater keeps reheating the loss. The waste is small next to the annoyance, but it is also a signal: a seal that leaks now will only open wider, so it is cheaper to swap a $5–25 part than to keep paying the meter.
Can I fix a dripping faucet myself?
Usually yes. Cartridge, ball, and ceramic-disc faucets all come apart with basic hand tools once you shut the supply stops, and a replacement cartridge or seat kit costs $5–25. The one rule that saves the job is matching the part exactly, so pull the old one first and take it to the store. If the valve seat is scored or the faucet body is corroded, a swap will not hold and you are into a full fixture replacement, which is where many people call a plumber.
Does high water pressure make faucets drip?
It does. Municipal pressure above 80 psi pushes water past seals that would seal fine at a normal 50–60 psi, so faucets drip, toilets run, and supply lines strain. A $10–15 gauge on a hose bib tells you in seconds. If the reading is high, a pressure-reducing valve set to 50–60 psi is the fix, and it protects the whole plumbing system, not just the one faucet you noticed.
How long should a faucet cartridge last?
A quality cartridge or washer set typically seals for 5–10 years before the rubber hardens and starts to weep, though hard water and hot-side use shorten that. A whole faucet usually lasts 15–20 years, so most homeowners rebuild the cartridge once or twice over a faucet's life rather than replacing the fixture. If you are swapping cartridges every year or two, suspect high pressure or a rough valve seat chewing them up.