Disposal Leaking
Updated February 20, 2026
Disposal leaks come from three places: top (sink flange), side (discharge pipe or dishwasher hose), or bottom (internal seal failure). Where it leaks tells you whether it is a simple fix or a replacement.
Overview
A leaking disposal causes cabinet damage, mold, and electrical hazards if water reaches the motor or outlet. Three leak locations, three different fixes. Top (where it meets the sink): flange seal or mounting hardware failed. Side: discharge pipe gasket or dishwasher hose connection is loose. Bottom: internal seals failed -- not repairable, needs replacement. Diagnosis is simple: dry everything, run water, watch where it appears first.
Symptoms
- Water dripping from the disposal body or connections under the sink
- Puddle on the cabinet floor centered beneath the disposal
- Dripping from the top where it meets the sink drain -- around the mounting ring
- Dripping from the side at the discharge pipe elbow or dishwasher hose connection
- Water seeping from the very bottom of the housing -- internal seal failure
- Musty smell or mold in the cabinet -- slow leak that has been going for a while
Common Causes
- Dried or loose flange putty -- the disposal connects through a mounting flange sealed with plumber's putty. Putty dries out, vibration loosens the mounting ring, water seeps between sink and flange.
- Loose mounting or snap ring -- the disposal hangs from the flange via a mounting ring. Vibration or impact loosens it, the unit drops slightly, breaks the seal. Snap ring comes loose and the whole assembly shifts.
- Worn discharge pipe gasket -- the rubber gasket between the discharge elbow and the disposal compresses and hardens over time, losing its seal. Leaks specifically when water drains through.
- Loose or cracked dishwasher hose -- the drain hose connects to the disposal with a hose clamp. Clamp loosens or hose cracks, water leaks during the dishwasher drain cycle.
- Internal seal failure (bottom leak) -- the motor shaft seal has failed. Water seeps from the very bottom of the housing. Not repairable on residential disposals. The unit needs replacement. Typical on 8-15 year old units.
What You'll Need
How to Fix It
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Identify the Leak Location
Clear under the sink, paper towels or newspaper below the disposal. Dry the entire exterior and all connections. Plug the drain, fill the sink 3-4 inches, pull the plug and watch with a flashlight. First sign of moisture tells you the location. Top: around the mounting ring. Side: discharge pipe flange or dishwasher inlet. Bottom: weeping from the housing itself.
Tip: Leak only when the dishwasher runs? The dishwasher hose connection is the source. Run the dishwasher and check during the drain cycle. -
Fix a Top Leak (Sink Flange)
Try tightening the mounting ring first -- clockwise from below, disposal wrench or tap the lugs with a screwdriver and hammer. Does not stop? Putty has dried out. Twist off the disposal, disconnect the discharge pipe, remove snap ring and mounting ring. Push the flange up through the sink. Scrape off all old putty from flange and sink surface. Fresh rope of plumber's putty around the flange, press back in, reassemble, remount.
Tip: Roll putty into a 1/2-inch rope, complete ring around the flange underside. Press firmly for full contact. Excess squeezes out when you tighten -- wipe it away. -
Fix a Side Leak (Discharge Pipe)
Remove the two bolts holding the discharge pipe flange. Pull off the elbow and rubber gasket. Flattened, cracked, or hardened? Replace it ($2-3, bring the old one to match). Clean both mating surfaces, install the new gasket, retighten bolts evenly. Snug is sufficient -- do not overtighten.
Tip: Gasket must be flat and centered before tightening. Misaligned gasket is the most common reason a discharge pipe leak comes back after repair. -
Fix a Side Leak (Dishwasher Hose)
Check the hose clamp -- tighten with a screwdriver or nut driver. Hose cracked, hardened, or not gripping? Replace it. Also check: was the dishwasher knockout plug removed when the disposal was installed? New disposal and the dishwasher has never drained right? The knockout (circular plastic disc inside the inlet) may still be in place. Screwdriver through the inlet, tap it out, retrieve from the grind chamber.
Warning: Knockout plug never removed but dishwasher has been draining? The plug may be partially dislodged, causing both leaks and drainage problems. Always check during any disposal repair. -
Diagnose a Bottom Leak (Internal Seal Failure)
Water from the very bottom (not from any visible connection) means the motor shaft seal has failed. No practical repair on residential units -- the seal is internal and not designed for replacement. Bottom leak means replacement. Less than 3-4 years old? Check the warranty -- most carry 2-5 years covering internal seal failure.
Tip: Before concluding bottom leak, make sure water is not running down from a top or side leak and dripping off the bottom. Dry everything, retest to confirm the actual origin. -
Replace the Disposal (If Internal Seal Has Failed)
Power off. Bucket under the unit. Disconnect discharge pipe and dishwasher hose. Twist counterclockwise to detach from the mounting ring (support the weight -- disposals are heavy). Same brand replacement? Existing flange and mounting ring usually reuse. New disposal aligns with the ring and twists clockwise to lock. Reconnect everything, restore power, test.
Tip: Match or exceed the old unit's horsepower. 3/4 HP handles most households. 1 HP for heavy use. Avoid 1/3 HP -- jams frequently and struggles with anything beyond soft food.
When to Call a Pro
Call a plumber if you are not comfortable replacing the unit, if the flange is corroded and will not seal with new putty, if the mounting hardware or snap ring is damaged, or if the leak is from a crack in the sink itself. A plumber replaces a disposal in 30-60 minutes.
Prevention Tips
- Check mounting ring tightness every 6 months. Vibration gradually loosens the connection.
- Inspect the dishwasher hose clamp annually. Vibration from both appliances loosens clamps over time.
- Disposal wobbles when you push on it from inside the sink? Tighten the mounting ring before the flange seal breaks.
- New installation? Generous plumber's putty on the flange. Too little putty is the top cause of leaks on new installs.
- Do not lean on the disposal or hang things from it when working under the sink. Loosens the mounting.
- Over 10 years old with a bottom leak? Replace promptly. Internal seal failure only gets worse.