Fix a Leaking Kitchen Sink Drain

Drips underneath your kitchen sink are a common nuisance that signal a failed seal or a hairline crack in your plumbing assembly. Ignoring these leaks leads to ruined cabinet bases, mold growth, and damaged flooring, making this a high-priority repair that requires only basic tools and a bit of patience. Performing this repair well involves more than just tightening a nut. It requires a clean workspace and an understanding of how slip-joint fittings seat against one another. When finished, you should have a bone-dry connection that remains secure even when you run a full basin of water through the line.

1. Clear Your Work Space. Empty your undersink cabinet completely to give yourself room to work. Place a shallow bucket or large bowl directly underneath the p-trap to catch the water remaining in the line.
2. Loosen the Trap Assembly. Loosen the plastic slip-joint nuts by hand, turning them counter-clockwise. If they are seized, use channel-lock pliers gently to provide extra leverage, being careful not to crack the plastic housing.
3. Clean Every Thread. Pull the trap sections apart and wipe away any hair, food buildup, or gunk from the pipe threads and the interior of the pipes. Use a stiff nylon brush if there is stubborn calcification inside the fittings.
4. Install Fresh Washers. Discard the old slip-joint washers, as they have likely lost their elasticity and sealing ability. Slide new rubber washers onto the pipe ends with the tapered side facing the direction of the joint connection.
5. Hand-Tighten the Nuts. Fit the pipes back together, ensuring the washers seat perfectly inside the joint before threading the plastic nuts back on. Hand-tighten the nuts until they feel snug and secure.
6. Verify the Seal Holds. Run cold water into the sink for one minute, then hot water for one minute, checking for drips at every joint. If a leak persists, tighten the nut only a quarter-turn more with pliers.