Leaking shut-off valve under the sink
Short answer
Most leaking sink shut-off valves drip from the stem when turned, from the packing nut, or from the compression nut where the pipe connects. A gentle snug of the packing nut often stops a stem leak. A valve that will not close fully, or leaks from the body, should be replaced; quarter-turn valves are a common upgrade.
In this guide
The small valves under sinks, often called angle stops, sit unused for years. Then you turn one, and it starts dripping. That is common, and usually easy to fix.
Where is it leaking?
| Leak location | Likely fix |
|---|---|
| Around the handle stem after turning | Tighten the packing nut slightly |
| At the outlet where the supply line connects | Tighten or replace the supply line |
| At the inlet where the valve meets the pipe | Snug the compression nut, or replace the valve |
| From the valve body | Replace the valve |
| Water still flows with the valve closed | Replace the valve |
Fixing a stem leak
- Hold the valve body steady with one wrench.
- Turn the packing nut, just behind the handle, about an eighth of a turn clockwise.
- Check for drips. Stop as soon as it stops leaking; overtightening makes the handle hard to turn.
Replacing the valve
Replacing a valve means shutting off the main water, draining the line and removing the old valve. Compression, push-fit and soldered valves each install differently. Many plumbers replace old multi-turn valves with quarter-turn ball valves, which are more reliable.
When to call a plumber
- The main water shutoff does not close fully
- The valve is soldered on, or the pipe behind it is corroded
- The leak is inside the wall
Replacing valves is often bundled with a faucet swap; see our faucet installation cost guide.
Multi-turn vs quarter-turn valves
| Valve type | Good to know |
|---|---|
| Multi-turn (compression stop) | Older style; rubber washer can harden and fail to seal |
| Quarter-turn ball valve | Opens or closes with a quarter turn; more reliable |
Quarter-turn valves are a popular upgrade because they close quickly in an emergency and rarely seize.
Common questions
Why did my shut-off valve start leaking after I turned it?
The packing around the stem dries out when unused. Turning the valve disturbs it and lets water seep out.
How often should shut-off valves be exercised?
Turning them once a year helps keep them working when you need them.
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