How to Fix a Leaking P-Trap Under Your Sink

P-traps are the unsung heroes of your home's plumbing, holding a small amount of water to block sewer gases from creeping into your living space. When you notice that telltale drip beneath your bathroom vanity, it usually isn't a sign of a major failure, but rather a loose fitting or a degraded gasket that has finally given up the ghost after years of temperature fluctuations. Fixing this is a rite of passage for any homeowner. You don't need a professional plumber to intervene here; with a basin wrench or just your own two hands, you can usually diagnose and solve the issue in less time than it takes to watch a sitcom. Done well, your sink will be dry and sealed, and you will have saved yourself a hefty service fee.

  1. Clear Your Work Zone. Remove all cleaning supplies and vanity storage items to give yourself a clear line of sight and room to work. Place a shallow bucket or a folded towel directly under the P-trap to catch the residual water trapped in the bend.
  2. Loosen Both Slip Nuts. Grip the plastic slip nuts on both ends of the U-shaped pipe and turn them counter-clockwise. If they are overtightened or stubborn, use a pair of slip-joint pliers with a cloth wrapped around the plastic to prevent cracking.
  3. Spot the Real Problem. Pull the trap down carefully, allowing the trapped water to drain into your bucket. Inspect the plastic threads for cracks and check the rubber washers for hardening or debris buildup.
  4. Scrub Away Mineral Buildup. Wipe the pipe ends and the interior of the slip nuts with a clean rag to remove mineral deposits or old pipe dope. Clean connections ensure a smooth, watertight seal when you reassemble.
  5. Install Fresh Rubber Washers. Slide new tapered rubber washers onto the pipe ends with the tapered side facing the joint where it will be compressed. Avoid reusing old, flattened washers as they rarely provide a reliable second seal.
  6. Seal and Verify. Reconnect the P-trap, tightening the slip nuts by hand until they are snug. Turn the sink faucet on at full pressure for one minute and watch closely for any moisture bead forming at the joints.