How to Fix a Leaking Sink Trap

Puddles under the sink are a universal homeowner grievance, usually signaling that the sink trap—the U-shaped pipe designed to hold a water seal—has lost its integrity. While it looks intimidating, the trap is essentially a simple assembly of plastic or metal pipes held together by threaded nuts and friction washers. When these connections vibrate loose or the seals harden over time, water drips onto your vanity floor, potentially causing structural water damage if ignored. Fixing this is a mechanical task that requires more patience than raw strength. Success lies in properly aligning the pipes to prevent cross-threading and ensuring that the rubber washers are seated firmly against the pipe faces. If you keep the area dry during the process and work methodically, you can restore a watertight seal in less than an hour without calling a plumber.

  1. Clear Your Workspace. Remove all items from the cabinet and place a shallow bucket or large towel directly beneath the trap. This catches the water that will inevitably spill once the pipe is opened.
  2. Loosen the Connection Points. Grip the slip nuts on either side of the U-shaped trap using your hand or channel-lock pliers if they are overtightened. Turn counter-clockwise until the nuts are loose enough to slide down the pipe, allowing the trap to drop away.
  3. Check for Wear and Damage. Remove the old rubber washers from the ends of the pipes. Check the pipe threads for cracks or debris and wipe them clean with a rag.
  4. Seat the New Washers. Slide the new slip nuts and then the new bevelled rubber washers onto the ends of the tailpiece and the drain arm. The bevelled side of the washer should face toward the trap connection.
  5. Reconnect the Trap. Position the U-shaped trap back into place and hand-tighten the slip nuts onto the threads. Ensure the trap is level and that the pipes are properly aligned before tightening.
  6. Test the Seal. Remove the bucket and turn on the faucet to run water at full pressure for at least one minute. Watch the connections closely for any signs of weeping.