How to Repair a Leaking Kitchen Sink Drain

Pipes hidden under the kitchen sink often suffer from years of minor vibrations and temperature fluctuations that loosen connections. A damp cabinet floor or a slow drip is a classic indicator that your slip-joint washers have hardened or that a plastic nut has cracked under pressure. Fixing this is a straightforward task that restores the integrity of your drainage system without requiring a professional. A successful repair relies on cleaning the existing pipe threads thoroughly and ensuring that the new gaskets sit perfectly flush within the pipe couplings.

  1. Clear the cabinet space. Empty everything from under the sink to gain full access to the piping. Place a bucket or a shallow tray directly beneath the suspected leak to catch any residual water when you loosen the joints.
  2. Unscrew the slip nuts. Use your hand or channel-lock pliers to unscrew the plastic or metal slip nuts connecting the P-trap to the drain tailpiece. Turn the nuts counter-clockwise to release the piping sections.
  3. Find the problem washer. Pull the P-trap free from the wall and tailpiece, allowing the water in the trap to drain into your bucket. Inspect the slip-joint washers, which are the small plastic or rubber rings located inside the nut connections.
  4. Scrub the joint clean. Use a damp cloth or a soft brush to remove soap scum, hair, and debris from the pipe threads and the seating areas where the gaskets rest. A clean surface is essential for the new washer to create an airtight seal.
  5. Swap in fresh washers. Slide the old washers off the pipes and install new ones, ensuring they are the correct size and facing the right direction. The tapered side of the washer should point toward the opening of the pipe it is entering.
  6. Reconnect with care. Reassemble the trap, threading the slip nuts on by hand until they are snug. Once hand-tight, turn them an extra quarter-turn with pliers, but be careful not to overtighten and crack the plastic.
  7. Verify the seal holds. Run cold water from the faucet for several minutes while watching each connection point closely. If you see a bead of water, give the nut another quarter-turn.