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Fix this week — tonight if the drip speeds upDIY difficulty: 2 / 5

Water pooling under the kitchen sink

Kitchen · Plumbing

You reported: A slow drip from the curved pipe under the sink; the cabinet floor is damp and a bucket fills about an inch overnight.

What it most likely is

Most likely a worn P-trap slip-joint washer or a loose compression nut. This is the single most common under-sink leak — and one of the few plumbing jobs that is genuinely DIY-friendly: no soldering, no supply-line pressure once the valves are off.

The decision

Do it yourself. Parts are under $20 and the job takes about half an hour.

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Do it yourself

$10–$25 in parts · 30–45 minutes

  1. 1Turn both shut-off valves under the sink clockwise until they stop. Run the faucet to confirm the water is off.
  2. 2Put a bucket under the P-trap (the U-shaped pipe) and loosen the two big plastic nuts by hand — expect a cup or two of water.
  3. 3Slide the trap off. Check the thin beveled washers on each joint; a cracked or flattened washer is almost always the culprit.
  4. 4Take the old washer to the hardware store and match it exactly (1-1/2 in is standard for kitchen sinks). Replace both washers while you're in there.
  5. 5Reassemble hand-tight, then a quarter-turn more with pliers — no more. Overtightening cracks the nuts.
  6. 6Turn the water back on, run the faucet for two minutes, and feel every joint with a dry paper towel. Any dampness means reseat that joint.

Tools and parts

  • • Bucket
  • • Slip-joint pliers
  • • Replacement P-trap washer kit (1-1/2 in)
  • • Paper towels
  • • Flashlight

Safety lines

  • • Shut the water off first — always. If a shut-off valve itself leaks or won't turn, stop: that valve is on the pressurized supply side and is a plumber job.
  • • No chemicals needed. Skip drain cleaner for a leak — it isn't a clog problem.

Stop and call a pro if… Call a plumber instead if: the leak is at the shut-off valve or the wall stub-out, you see mold or cabinet rot spreading, or the drain line itself is cracked. Austin plumbers typically charge $150–$300 for a trap replacement visit (sample range).

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