How to Repair a Leaking Sink Drain Pipe

Pipes under your sink represent a simple but critical network that manages waste and keeps sewer gases out of your home. When you see water pooling in the cabinet, it usually points to a failing connection or a degraded seal within the P-trap assembly. Ignoring a small drip inevitably leads to water damage in the cabinetry, mold growth, or a sudden, larger failure that causes significant flooding. Done well, this repair is a clean, dry, and permanent fix that prevents future headaches. The goal is to restore a watertight seal without over-tightening plastic components, which can easily crack or warp. You do not need to replace the entire plumbing system; you simply need to address the failing point of contact where water escapes under pressure or gravity.

  1. Set up dry ground. Empty all items from under the sink and place a bucket or a large plastic basin directly beneath the P-trap. This captures the standing water that will inevitably spill once you loosen the pipes.
  2. Break the seal slowly. Use tongue-and-groove pliers or a pipe wrench to gently loosen the plastic slip nuts on both ends of the U-shaped P-trap. Turn counter-clockwise until you can finish the job by hand.
  3. Find the failure point. Pull the trap section free and pour the residual water into your bucket. Inspect the slip joint washers inside the connections for cracks, hardening, or general wear.
  4. Prep surfaces perfectly. Wipe down the threaded ends of the sink tailpiece and the wall pipe with a clean rag. Ensure no debris or old plumber's tape remains, as these prevent a new washer from sitting flush.
  5. Install fresh seals. Slide the new slip joint washers onto the pipes, ensuring the tapered side faces the direction of the connection. Properly oriented, these create the seal that prevents water from escaping the joint.
  6. Verify the fix works. Slide the P-trap back into position and tighten the slip nuts by hand until they are snug. Turn on the faucet and run water for two minutes while watching closely for any new drips.