Symptoms
- Drip coming from a threaded connection below the disposal
- Leak worsens when the disposal or sink drains
- Visible gap or looseness at a joint
- Water trail leads to a specific connection point
Likely causes
- CommonLoose slip nut at a trap or extension pipe jointThese nuts can loosen over time from vibration and thermal cycling.
- CommonMissing or worn slip joint washerThe rubber or plastic washer inside the nut seals the joint and wears out over years.
- PossibleMisaligned pipes putting stress on a jointPipes that don't line up evenly can leak even when tightened.
- Less commonCracked pipe near the jointOld, brittle plastic pipe can crack right at the threaded section.
What to do
- Place a bucket under the joint and turn off water to the sink if accessible, or work with the disposal off and dry.
- Locate the specific leaking slip joint by drying everything and running water while watching closely.
- Hand-tighten the slip nut first; many leaks are simply a nut that backed off slightly.
- If tightening doesn't stop it, loosen the nut, check the washer inside for cracks or flattening, and replace it if needed.
- Reassemble making sure pipes are pushed together fully and aligned straight before tightening the nut.
- Run water again and check the joint is now dry before considering it done.
Tools and parts
- Adjustable pliers or channel-lock pliers
- Bucket
- Replacement slip joint washer
Slip joint washer kitSearch: “sink drain slip joint washer kit”
When to call a pro
If tightening and replacing the washer doesn't stop the leak, or the pipe itself looks cracked, a plumber can replace the section.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.