Stop a Leaking P-Trap Under the Sink

Kill the drip fast with a fresh washer and simple alignment.
Difficulty: Easy
Success Rate: 90%
Cost: $0 - $20
Estimated Timeline: 10–20m
Turn Off Water: No
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Tools Needed:

  • Bucket

  • Slip-joint pliers or adjustable wrench

  • Flashlight

  • Towels or rags

Materials / Parts:

  • Slip-joint washer (1-1/4″ bath or 1-1/2″ kitchen) — 1 — ~$1–$3

  • Optional: replacement slip-joint nut — 1 — ~$2–$4

  • Optional: complete P-trap kit (if parts are cracked or corroded) — 1 — ~$8–$15

Safety Warnings:

  • Wear gloves; edges on old metal can be sharp.

  • Do not run water while the trap is apart.

  • If you smell sewer gas after reassembly, stop and re-seat the trap seal.

Test & Verify:

  • Dry the joint and check again after 2 minutes.

  • Fill the sink, then drain it and inspect for leaks.

  • Wipe the pipe and confirm it stays dry.

Cleanup & Disposal:

  • Empty the bucket. Wipe the cabinet floor dry.

  • Throw away the old washer with household trash.

Pre-Checks:

  • Confirm the leak point (nut at trap bend, trap arm, or tailpiece).

  • Note pipe size (1-1/4″ or 1-1/2″) to match the washer.

  • Place a bucket under the trap to catch water.

  • Dry the fittings so new leaks are easy to spot.

Step-By-Step Instructions:

  1. Put the bucket under the trap.

  2. Hand-loosen the slip nut at the leaky joint. Use pliers only if needed.

  3. Lower the trap bend and drain water into the bucket.

  4. Remove the old washer. Clean the mating surfaces.

  5. Seat a new washer with the tapered side toward the joint.

  6. Refit the trap parts. Align them straight and square.

  7. Hand-tighten the slip nut. Add a quarter-turn with pliers. Do not over-tighten.

  8. Check that the trap arm slopes slightly toward the wall.

  9. Run water for 10–15 seconds. Watch the joint for beads of water.

  10. If it weeps, nudge alignment, then re-tighten by a small amount.

When to Stop & Call a Pro:

  • The trap or nuts are cracked or rust-thin.

  • The wall elbow spins or feels loose in the wall.

  • Sewer odor persists after a proper water seal.

  • Threads are stripped and will not tighten.

Common Mistakes:

  • Over-tightening slip nuts and deforming the washer.

  • Misaligned trap parts causing a side load and leaks.

  • Using the wrong washer size.

  • Forgetting to support the trap while tightening.

Troubleshooting:

Q: It still drips at the tailpiece.
A: Replace the tailpiece washer and re-seat the trap.

Q: The nut bottoms out but still leaks.
A: Washer may be flipped or wrong size; reinstall with the taper facing the joint.

Q: Water gurgles after the fix.
A: The trap may be partly blocked; remove and clean the trap bend.

Q: I smell sewer gas.
A: The trap may be dry or mis-seated; run water to fill the trap and re-seat the joints.