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How to fix a sink leak

We'll locate the leak, fix the faucet or connections, and tell you when to call a plumber.

How-to · Home plumbing
20–45 min
What you'll need
  • Replacement faucet washers or cartridge (for your faucet type)
  • Replacement supply lines (if needed)
  • Plumber putty (for drain flange)
  • Channel-lock pliers, screwdriver
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Steps

Goal: Shut off water, locate the leak, fix the faucet or connections, and know when to call a plumber.

  • Turn off the hot and cold water supply valves under the sink. Relieve pressure by opening the faucet until water stops.
  • Good: No water flow when the faucet is open. Proceed to Locate the leak.
  • Bad: Water still flows—find the correct shutoff valves.

Locate the leak

Goal: Identify where the water is escaping.

  • Dry the sink, faucet, and area under the sink. Turn the water back on and run the faucet.
  • Watch where water appears—at the faucet spout or base, at the supply lines, at the drain flange, or at the P-trap.
  • Good: You see water emerge from one or more spots. Proceed to Fix faucet or Tighten connections based on location.
  • Bad: Cannot locate the leak—call a plumber.

Fix faucet

Goal: Stop leaks at the faucet (drip when off).

  • For compression faucets, remove the handle and replace the stem washer. For cartridge faucets, replace the cartridge. For ball faucets, replace the seats and springs. Check your faucet type and replace the worn parts.
  • Good: No drips when the faucet is closed. Proceed to Verification.
  • Bad: Faucet body is cracked—replace the faucet or call a plumber.

Tighten connections

Goal: Stop leaks at the supply lines or P-trap.

  • If the leak is at the supply lines, shut off the water. Check that the lines are fully threaded and the nuts are snug. Tighten the nuts a quarter turn—do not overtighten. If the lines are cracked, replace them.
  • If the leak is at the P-trap, tighten the slip nuts a quarter turn. If the leak is at the drain flange, remove the drain and reapply plumber putty or a new gasket.
  • Good: No drips at the connections. Proceed to Verification.
  • Bad: Connections will not seal—call a plumber.

When to get help

Call a plumber if:

  • The faucet body is cracked.
  • The leak is behind the wall.
  • You cannot locate the source.
  • You are not comfortable with the repair.

Do not overtighten connections—you can damage fittings.

Verification

  • No drips at the faucet, supply lines, drain, or P-trap when the water is on.
  • The sink drains normally and the area under the sink stays dry.

Where is the leak?

Dry the sink and area under it. Run the faucet. Watch for water at faucet, supply lines, drain, or P-trap.

Shut off the water. Dry the sink and area. Turn water on and run the faucet. Good: you see water at the faucet, supply lines, drain, or P-trap. Bad: cannot locate—call a plumber.

Faucet Supply lines or drain

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Replace washers or cartridge

Replace faucet washers or cartridge per your faucet type. Turn water on. Good: no drip. Bad: faucet body cracked—replace faucet or call a plumber.

Done

Tighten supply lines or P-trap

Tighten supply line nuts or P-trap slip nuts. Fix drain flange if drain leaks. Turn water on. Good: no leak. Bad: still leaks—call a plumber.

Done

Reviewed by Blackbox Atlas

Frequently asked questions

Why does my sink leak?
Common causes: worn faucet washers or cartridges, loose supply line connections, a loose drain flange, or a loose P-trap. The faucet drips when washers or cartridges wear; supply lines and the P-trap can loosen over time.
Can I fix a sink leak myself?
Yes. Most leaks at the faucet, supply lines, or P-trap are fixable by replacing washers, tightening connections, or fixing the drain seal. Shut off the water first. If the faucet body is cracked, replace the faucet or call a plumber.
When should I call a plumber for a sink leak?
Call a plumber if the faucet body is cracked, the leak is behind the wall, or you cannot locate the source. Do not overtighten connections—you can damage fittings.

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