Direct answer: If water is showing up where the garbage disposal meets the sink, the usual cause is a failed seal at the sink flange or a mounting assembly that has loosened up. Most of the time the disposal body is fine.
Most likely: Start by drying everything completely, then confirm the leak starts at the top rim of the disposal when you run water. If it does, the sink flange seal or disposal mounting assembly is the first place to work.
A true sink flange leak shows up right at the top of the disposal, under the sink bowl, usually while water is running from the faucet. Reality check: this is one of the more common disposal leaks, and it is often fixable without replacing the unit. Common wrong move: tightening random screws before you prove where the water actually starts.
Don’t start with: Do not start by replacing the whole garbage disposal just because water is dripping off the bottom. A top leak often runs down the housing and fools people.
The first wet spot forms right under the sink opening where the disposal mount meets the sink.
Start here: Dry the flange area fully and run a small stream of water to confirm the leak starts there, not at the dishwasher inlet or drain elbow.
No drip when the sink is idle, but water appears quickly once you run water into the basin.
Start here: That points strongly to the sink flange seal rather than an internal disposal housing leak.
Water drips off the bottom of the disposal, but the housing above is wet too.
Start here: Wipe the whole unit dry and watch the top edge first. Top leaks commonly track down the shell.
The disposal worked, then leaked soon after being installed, reset, or twisted off and back on.
Start here: Suspect a flange that was not seated well, putty that did not seal, or a mounting ring that did not lock evenly.
This is the most common reason for a leak at the sink opening. The seal can dry out, shift, or never seat correctly after installation.
Quick check: Dry the underside of the sink around the flange and run water around the drain opening. If the first bead forms right under the flange lip, the seal is likely bad.
If the disposal is not pulled tight and evenly against the flange, water can slip past the seal even when the putty is still usable.
Quick check: With power off, check whether the disposal body has any sag or twist and whether the mounting hardware looks uneven or backed off.
Sometimes the leak starts above the sink where the flange meets the sink surface, then works down underneath.
Quick check: Look in the sink bowl while water runs. If you see water creeping around the metal flange edge, the flange needs to be resealed.
A small hose or elbow leak can spray or run along the disposal and make the top area look guilty.
Quick check: Dry the dishwasher inlet, discharge elbow, and upper housing, then run water and watch with a flashlight for the first wet point.
You need the first wet spot, not the last drip. Disposal leaks travel.
Next move: If the first wet spot is right under the sink flange, stay on this page and check the mount and seal next. If the first wet spot is at the dishwasher inlet, drain elbow, or the disposal body seam, this is not really a sink flange leak.
What to conclude: A true flange leak starts at the top connection between the sink and the disposal mount. Anything lower is a different repair.
A disposal that is not locked up tight can leak at the flange even when the disposal itself is fine.
Next move: If the leak stops after the mount is tightened evenly, monitor it for the next few sink uses. If the mount is tight but water still starts at the flange, the seal itself is the likely problem.
What to conclude: Loose hardware can let the flange shift just enough to break the seal. If tightening changes nothing, resealing is usually next.
A bad seal often shows itself from the sink side before you take anything apart.
Next move: If this test clearly reproduces the leak, you have enough evidence to stop guessing and reseal the flange. If no leak shows with a small ring of water, run a fuller stream and recheck the dishwasher inlet and discharge elbow for a lookalike leak.
Once you have confirmed the leak starts at the flange, resealing is the repair that usually solves it.
Next move: If the area stays dry during a faucet test and again during a normal sink use, the repair is done. If it still leaks from the same top seam after a careful reseal, the mounting assembly may be warped or damaged and should be replaced.
When a confirmed flange leak survives a proper reseal, damaged mount parts are the most likely remaining disposal-side cause.
A good result: If the top seam stays dry, the mounting assembly was the failed part.
If not: If water still appears from the disposal body seam or lower shell, move to a bottom-leak diagnosis and do not keep replacing flange parts.
What to conclude: A mount that cannot hold even pressure will keep leaking no matter how many times you redo the putty. Once the top is proven dry, any remaining leak is somewhere else.
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Because water from a top leak runs down the outside of the disposal housing and drips off the lowest point. Dry the whole unit first and watch for the first place that turns wet.
Sometimes, yes, if the mounting assembly has loosened slightly. But if the putty seal has failed or the flange is damaged, tightening alone usually will not hold for long.
Usually not. A true sink flange leak is commonly a seal or mounting issue above the disposal body. Replace the disposal only if the housing itself is leaking or the unit has other major problems.
That strongly points to the sink flange area or another drain connection, not the motor section. Water-flow-only leaks are usually easier to trace because you can test them with the disposal powered off.
Plumber's putty is common for many sink flange installs, but sink material matters. If you are working with a surface that can stain or has special sealing requirements, confirm the right seal method before reinstalling the flange.
If you can tighten it evenly and the disposal still will not sit square, lock firmly, or stay dry after a proper reseal, the mount may be warped, cracked, or stripped. That is when replacement makes sense.