A garbage disposal leaking from the top almost always traces back to the sink flange, the metal ring that connects the disposal to the drain opening in your sink basin. That’s the part that sits in the sink and seals against the porcelain or stainless with plumber’s putty underneath. When that seal fails or the flange loosens, water leaks down the outside of the disposal housing, which makes it look like the unit itself is cracking open. It usually isn’t.
What the Sink Flange Actually Does
The flange is a short metal collar that drops into your drain opening from above. A bead of plumber’s putty seals it to the sink surface. Below the sink, three mounting bolts clamp a lower mounting ring to the flange body, and that ring is what the disposal twists onto. A snap ring seats in a groove at the bottom of the flange and keeps the mounting ring from sliding off before the bolts are tightened.
The flange sits in water every time the sink runs. Over years, vibration from the motor, repeated impacts from stuffing food down, and minor plumbing shifts work the bolts loose. When they loosen, the flange can tilt slightly or pull away from the sink, and the putty seal breaks.
Why Top Leaks Get Confused with Other Leaks
Disposals can leak from three places: the top (the flange), the side (the dishwasher drain nipple or the drain discharge elbow), or the bottom (internal seals). Each one is a different problem.
If water is dripping straight down from the center of the unit or pooling at the base, that’s usually a bottom leak from worn internal seals, and the fix is typically replacing the unit. If water is running along the side toward a hose connection, that’s the dishwasher drain or the drain elbow. If water is weeping down from the very top of the unit, or you see it seeping up around the drain opening in the sink, that’s a flange problem.
You can confirm it by drying everything under the sink, then filling the sink with a few inches of water without running the disposal. Watch where the drip starts. If it shows up while the water just sits there, before you even run the unit, the flange or putty seal is your answer.
How a Plumber Diagnoses and Fixes It
A licensed plumber will pull the disposal off the mounting assembly first. That involves disconnecting the drain line, removing the dishwasher drain if present, and twisting the unit free from the mounting ring. Sometimes the fix is just retightening the three mounting bolts if they’ve worked loose. More often, the old putty has dried out or cracked, and the plumber cleans it off, re-rolls a fresh bead, reseats the flange, and retightens everything in sequence so the flange sits level.
If the flange itself is corroded or the snap ring is deformed, they’ll swap in a new flange kit. Most fit standard 3.5-inch drain openings.
The whole job involves working in a tight cabinet space, holding weight overhead, and reconnecting drain lines that need to stay watertight. Drain connections get broken and remade in the process, which is where leaks get introduced if the work isn’t done carefully.
One Check Before You Call
Before you dial anyone, reach under the sink and try snugging the three mounting bolts on the mounting ring by hand. If the flange was simply knocked loose rather than deteriorated, that sometimes stops a small seep. It costs nothing and takes a minute.
That’s the limit of what makes sense without a license. Everything beyond it, reseating the flange, rolling fresh putty, disconnecting and reconnecting drain lines, requires removing the disposal and disturbing the P-trap. One slip there and you trade a surface drip for a slow leak inside the cabinet wall. That’s a worse problem.
If the disposal is ten or more years old, mention it when you call. The plumber may recommend replacing the unit while the drain connections are already apart, which saves a return trip.
Call a Licensed Plumber
If snugging the bolts doesn’t stop the drip, or if the flange visibly moves in the drain opening, or if you see corrosion on the flange or housing, the job needs a licensed plumber. Same goes if you’re at all unsure about the drain connections.
Any work that touches drain plumbing under a California sink requires a licensed contractor. Verify the license at cslb.ca.gov before anyone starts. Enter the name or license number and confirm it’s current and in the right classification.
This site is an information guide only. It does not hold a plumbing license and does not offer plumbing services. The point of this article is to help you understand what’s happening before you call, so the conversation with your plumber is productive. A top leak is usually a flange seal, not a cracked unit. That’s a straightforward job for someone licensed to do it.