How to Repair a Leaky Sink Trap

P-traps serve as the silent sentinels of your home plumbing system, holding a small pool of water to block sewer gases from drifting into your kitchen or bathroom. When you notice a puddle forming beneath the cabinet, it is usually a sign that the compression seals have hardened over time or the connections have vibrated loose from regular use. Fixing a leak here is a rite of passage for any homeowner. It is a messy job that requires little more than a bucket and a fresh set of washers. By systematically checking the connection points and ensuring the drain pipes are properly aligned, you can restore a bone-dry cabinet floor in under an hour.

Clear the workspace first. Empty everything from underneath the sink so you have clear visibility and room to maneuver. Place a shallow bucket or a stack of old towels directly beneath the trap to catch the water that will drain out once you loosen the pipes.
Tighten before you disconnect. Before dismantling anything, try tightening the plastic slip nuts by hand in a clockwise direction. If they won't budge, use your pliers very gently to turn them just a quarter-turn further to see if the leak stops.
Remove the trap assembly. Unscrew the slip nuts connecting the U-shaped trap to the tailpiece coming from the sink and the drain pipe exiting the wall. Tilt the trap carefully to pour the remaining water into your bucket.
Swap the washers out. Remove the old rubber slip-joint washers from the ends of the pipes. Slide on new washers, ensuring the tapered side faces toward the connection point where the pipe meets the nut.
Hand-tighten and align. Slide the trap back into place, ensuring the pipes are aligned perfectly straight without tension. Thread the slip nuts onto the pipe ends by hand until they are snug.
Test for the dry seal. Run cold water from the faucet for two minutes while observing the connections for any moisture. Dry the area thoroughly with a paper towel and check again for wet spots to confirm the seal is airtight.