Symptoms
- Puddle or drip under the sink near the curved pipe
- Cabinet floor damp specifically near the trap
- Leak worse when water is running or right after draining
- Visible corrosion or mineral crust on the trap
Likely causes
- CommonLoose slip nut connectionThe nuts that join trap sections can loosen over time from vibration or being bumped.
- CommonWorn or missing slip nut washerThe rubber or nylon washer inside each connection seals the joint and wears with age.
- PossibleCracked trap from age or impactPlastic traps can crack if stepped on or hit while storing items under the sink.
- PossibleCorroded metal trapOlder metal traps can corrode through over many years.
What to do
- Place a bucket under the trap and dry the area completely.
- Run water and watch closely to find the exact point of the leak.
- If it's at a slip nut, hand-tighten it first, then use pliers for an extra quarter turn if needed, avoiding overtightening plastic fittings.
- If tightening doesn't stop it, disconnect that joint, inspect the washer, and replace it if worn, flattened, or missing.
- If the trap itself is cracked or heavily corroded, replace the entire trap assembly, which is inexpensive and simple to install.
- Reassemble all connections hand-tight plus a partial turn with pliers, then run water again to confirm the leak is fixed.
- Wipe out the cabinet and let it dry fully to prevent mold or warping.
Tools and parts
- Adjustable pliers
- Bucket
P-trap assembly kitSearch: “sink P-trap replacement kit”
When to call a pro
Call a plumber if the leak is at a joint connecting to the wall drain pipe itself, since that connection can be trickier to seal correctly.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.