Leaky Garbage Disposal Fix: The Flange Seal Nobody Checks
That puddle under your sink almost never means a new disposal—it means the flange seal between the sink and unit has broken down and needs to be reset.
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When water pools under the sink near your disposal, most people assume the unit itself is failing and start pricing replacements. But the actual leak point in the vast majority of cases is the plumber's putty seal at the sink flange—the ring where the disposal mounts to the sink drain opening. Over years of heat cycles and moisture, that putty dries out, shrinks, and stops gripping, letting water seep down the flange threads instead of draining through the pipe. Re-seating the flange with fresh putty and even torque on the mounting bolts is what actually stops the leak—not tightening the disposal's side connections, which rarely fix a leak coming from above.
What You'll Need
- Plumber's putty, about $4
- Adjustable pliers or disposal wrench, likely already on hand
- Bucket, to catch drips during removal
- Clean rag, for wiping old putty residue
- Flashlight, to inspect the flange gasket
- Replacement rubber gasket (if cracked), around $6
How to Build It
- Shut off power to the disposal at the breaker before touching anything underneath the sink.
- Support the disposal unit and loosen the mounting ring to drop it away from the sink flange.
- Remove the old flange from above the sink and scrape away every bit of hardened, cracked putty.
- Inspect the rubber gasket beneath the flange for cracking or flattening, and swap it if it's lost its spring.
- Roll a fresh rope of plumber's putty and press the flange back into the sink opening firmly and evenly.
- Reattach the mounting ring from below and hand-tighten the three mounting screws evenly, in a star pattern, not one at a time.
- Lift the disposal back into place and lock it onto the mounting ring, then wipe away squeezed-out excess putty from the sink surface.
- Run water for five minutes while checking underneath with a flashlight for any new drips before calling it done.
Skip the tube of clear silicone sealant that some hardware stores push for this job—plumber's putty stays pliable so you can remount the flange later, while silicone cures rock-hard and turns your next repair into a chisel job.
