How to Fix a Leaking P-Trap Under Your Sink

P-traps are the U-shaped sections of pipe under your sink designed to hold a small amount of water, which acts as a barrier against sewer gases entering your home. When you notice a drip or a puddle inside the vanity, it is almost always due to a dried-out washer or a loose connection caused by years of minor expansion and contraction. Fixing this is a classic plumbing chore that requires no specialized equipment and very little time. Done well, your pipes will be bone-dry and sealed tight without the need for pipe dope or chemical sealants, which shouldn't be necessary on modern slip-joint fittings.

1. Clear the workspace first. Empty everything out from under the sink and place a bucket or deep pan directly beneath the P-trap. This catches the water remaining in the trap once you loosen the connections.
2. Free the slip nuts gently. Use tongue-and-groove pliers or your hands to turn the plastic slip nuts at both ends of the U-bend counter-clockwise. If they are tight, wrap a rag around them to get a better grip before applying force.
3. Examine the culprit. Pull the U-bend away from the tailpiece and the wall pipe. Inspect the interior for blockages and check the rubber washers for cracks, hardening, or signs of decay.
4. Swap in fresh washers. Slide the old washers off the pipe ends and discard them. Install new tapered rubber washers, ensuring the tapered (beveled) side faces toward the fitting you are connecting to.
5. Put it back together. Slide the U-bend back into position, ensuring it is aligned with both the sink tailpiece and the wall drain pipe. Thread the slip nuts onto the fittings by hand until they are snug.
6. Verify the seal holds. Turn on the faucet and let water run through the trap for at least two minutes. Check for any moisture around the nuts, then tighten an additional quarter-turn with pliers if necessary.