How to Fix a Leaking Sink P-Trap

Pipes beneath your sink perform a vital, invisible job, keeping sewer gases out of your home while managing wastewater. When you notice that telltale puddle forming in the cabinet, it is usually a sign that a connection has vibrated loose or a gasket has reached the end of its lifespan. Dealing with this early prevents water damage to your cabinetry and stops small drips from becoming costly structural headaches. Fixing a P-trap is a classic rite of passage for any homeowner. The setup is designed to be disassembled by hand, meaning you rarely need heavy machinery or specialized knowledge to get it back in order. Success here looks like a dry cabinet floor and a joint that holds pressure without a single bead of moisture forming after a full sink basin is drained.

Clear the Cabinet Space. Empty everything from underneath the sink to give yourself room to work. Place a bucket or a shallow pan directly beneath the P-trap to catch the water that will inevitably spill when you loosen the pipe.
Crack the Slip Nuts Loose. Grasp the slip nuts on either side of the U-shaped trap by hand. Turn them counter-clockwise to loosen, using tongue-and-groove pliers only if they are stuck fast.
Disconnect the P-Trap. Slide the trap downward and off the tailpiece and the wall pipe. Pour the water trapped inside the U-bend into your bucket.
Wipe All Threads Clean. Wipe the threads of the pipes and the slip nuts clean with a rag. Remove any old, crusty plumber's putty or mineral buildup from the seating surfaces.
Swap in Fresh Washers. Slide the old washers off the pipe ends and replace them with new slip-joint washers of the matching size. Ensure the tapered side of the washer faces the direction of the joint connection.
Reassemble and Hand-Tighten. Slide the trap back into place, ensuring the washers seat squarely against the pipe lips. Hand-tighten the slip nuts firmly, then give them a final quarter-turn with your pliers.
Run the Final Leak Test. Run a full sink of water and let it drain rapidly into the trap. Inspect every connection point with a dry paper towel to check for hidden drips.