How to Stop a Leak Under Your Kitchen Sink

Puddles under the kitchen sink are never a welcome sight, but they are rarely a plumbing emergency if you act quickly. The cabinet floor acts as a basin, catching drips that can ruin particle board or harbor mold if left unchecked. A well-executed repair starts with clear visibility and a methodical approach to tracing the water back to its origin. Most sink leaks stem from loose fittings, aging rubber gaskets, or a compromised P-trap. When you perform this repair, aim for a 'snug-but-not-stripped' fit. Overtightening often cracks plastic nuts or pinches washers out of position, which creates a new leak in the process. With the right focused attention, you can usually stop the dripping in under an hour without calling a professional.

  1. Clear the Cabinet Completely. Remove all cleaning supplies and items from under the sink. Wipe the pipes and the cabinet floor completely dry with rags to help you spot exactly where the fresh water beads appear.
  2. Spot the Drip Origin. Turn on the faucet and run water down the drain while using a flashlight to watch the joints. Check the slip nuts on the P-trap, the basket strainer connection, and the supply line fittings.
  3. Tighten the Joints Gently. If the leak is at a plastic pipe joint, try tightening the nut by hand first. If it remains loose, use channel-lock pliers to give it a quarter-turn, being careful not to crack the plastic.
  4. Swap Out the Washer. If tightening doesn't stop the drip, unscrew the nut and inspect the rubber slip-joint washer inside. Remove any debris, replace it with a new washer of the identical size, and reconnect the joint.
  5. Install the New P-Trap. If the plastic pipes are warped or cracked, loosen all slip nuts and remove the old P-trap assembly. Slide the new trap into place, ensuring all gaskets are seated flat before hand-tightening the nuts.
  6. Verify the Fix Holds. Run the faucet at full volume for three minutes while watching every joint you touched. If no water beads form, wipe the pipes down once more and return your items to the cabinet.