Quick Answer:
Dry the cabinet floor, run water while watching each joint (sink flange, mounting ring, discharge elbow, dishwasher inlet). Lightly snug slip nuts by hand and, if the discharge elbow keeps dripping, reseat the rubber gasket. If the leak is at the sink flange or near wiring, stop and call a professional.
Why This Happens
New disposals use a few rubber seals and slip-fit connections. During the first rinse you can find small gaps that weren’t obvious during installation: a gasket not seated, a slip nut left slightly loose, or a dishwasher inlet clamp not tight. Vibration during testing also shifts parts. Small leaks are common and often fixable with simple checks; if the leak is at the flange or electrical area it’s more serious.
Step-by-Step What to Do
1. Clear and dry the area
- Open the cabinet and remove anything stored under the sink.
- Wipe the cabinet floor and the disposal body dry with towels so you can see fresh drops appear.
2. Run water and watch each joint
- Turn the hot water on to a steady stream and let it run while you watch every connection point: the sink flange at the top, the mounting ring where the unit hangs, the discharge elbow where the pipe connects, and the dishwasher inlet/hose fitting.
- Have a bucket or towel ready for catches and watch carefully for where the first drops form.
3. Lightly snug slip nuts by hand
- If a slip nut at the discharge elbow or drain tailpiece weeps, try tightening it by hand a quarter-turn to a half-turn—just snug, not forceful.
- If needed, use pliers for a final small turn but avoid large, forceful twists.
4. Reseat the discharge gasket
- If the elbow continues to drip, loosen the nut, slide the elbow off, check the rubber gasket for folds or misalignment, press it back into place squarely, then reattach and hand-tighten the nut.
- After reseating, run water again and watch for leaks.
5. Recheck the sink flange and mounting ring
- If water appears at the top near the sink, check the sink flange seal and mounting ring alignment—small gaps here can drip into the cabinet.
- Do not force or wobble the mounting hardware; if the flange is the source, consider professional help.
6. Test dishwasher inlet
- If the leak shows at the dishwasher connection, tighten the hose clamp or re-seat the hose. Run a short cycle on the dishwasher to confirm the fix.
What Not to Do
- Don’t overtighten plastic slip nuts or clamp fittings—warped washers can leak worse if you strip or deform them.
- Don’t stick your hands into the disposal or run it while you’re working on connections.
- If the leak is at the sink flange or electrical area, professional help is appropriate; attempting major flange or wiring work yourself can cause bigger damage.
When to Call a Professional
Call a plumber if:
- The leak comes from the sink flange or the mounting hardware at the top of the unit.
- Water is contacting wiring or the disposal’s electrical junction box.
- You can’t stop the leak after hand-tightening and reseating gaskets, or if parts look cracked or stripped.
Safety Notes
- Turn off power to the disposal before working on any connections—either unplug it or switch off the circuit breaker.
- Wear gloves to protect hands from sharp sink edges and metal parts.
- Do not run the disposal while you are checking or tightening fittings.
Common Homeowner Questions
- Why does water only appear when the dishwasher runs?
Likely the dishwasher inlet hose or its clamp is loose or misaligned; check that hose and its clamp for tightness and proper seating. - Should I use plumber’s putty around the sink flange?
Follow the disposal and sink manufacturer’s instructions—some flanges use putty or silicone. If unsure, call a pro to avoid voiding warranties. - Is it safe to use the disposal after I stop the leak?
Yes, once all connections are dry, properly seated and hand-tight, and the power is restored safely, normal use is fine.
If your sink still backs up or you hear noises after fixing the leak, check these related topics: Sink backs up after disposal install and Gurgling after disposal install.