Referral service, not a contractor. Prevent Home Leaks does not perform plumbing, leak repair, or water damage restoration. We may be paid if you hire a provider through a partner link. Always confirm the provider's license and get a written estimate. How this works
Finding and fixing leaks under the sink
Trace it with dry paper towels
- Empty the cabinet and dry every pipe and fitting.
- Wrap dry paper towel around each joint.
- Run water in the sink (to test the drain) and separately turn the faucet on and off (to test the supply). The first towel to get wet shows the source.
Common sources
- Drain slip nuts on the P-trap: hand-tighten, or replace the slip washer if it's cracked.
- Supply lines between the shutoff valve and the faucet: replace braided supply lines that are corroded or kinked.
- Shutoff (angle stop) valves: a drip at the stem may stop with a slight snug of the packing nut. Older multi-turn valves are often replaced with quarter-turn valves.
- Faucet base or sprayer hose: water running down from above the counter.
- Dishwasher or disposal connections in kitchens.
Call a pro if
The leak is from inside the wall, the shutoff won't close, or the cabinet floor is soft or moldy. That can mean a long-running leak and hidden damage (see hidden leak signs).