What the flange does
The flange sits in the sink's drain hole and seals against the sink with plumber's putty. A mounting assembly beneath the sink clamps it tight, and the disposal hangs from that assembly. If the seal fails, water runs down the outside of the flange and drips through the cabinet.
Many leaks blamed on the disposal are in fact flange leaks. Before you replace anything, run water into the sink with the disposal off and look at where the drip first appears.
Find the real leak first
| Where the water appears | Likely cause | Fix |
|---|---|---|
| Ring under the sink, just below the sink bowl | Flange putty seal failed | Reseat the flange with fresh putty |
| From the side of the disposal body | Housing crack or internal seal | Replace the disposal |
| From the drain elbow | Loose or worn gasket | Replace the gasket and tighten |
| From the dishwasher hose | Hose clamp or knockout plug | Reconnect or replace |
If the housing is cracked, a new flange will not help and replacement is the only fix. Our garbage disposal repair page covers that case.
What you need
- Plumber's putty, not silicone, for the flange seal.
- A screwdriver and, for some models, a hex key.
- A pair of slip-joint pliers or a channel lock.
- A bucket and towels.
- The new mounting kit that matches your disposal model, which is usually in the box.
Replacing the flange, step by step
Power off and disconnect
Unplug the disposal or switch off the breaker. Disconnect the drain elbow and dishwasher hose and release the disposal from its mount.
Remove the old flange
Loosen the mounting ring and snap ring, push the flange up and clear the old putty from the sink.
Seat the new flange
Roll a rope of putty, press it under the flange lip, set it in the drain hole and press down firmly.
Mount and test
Install the gasket, backup ring and mounting ring under the sink, tighten evenly, trim the excess putty, reattach the disposal and run water to test.
Tighten the mounting screws evenly, like the lug nuts on a wheel. An uneven clamp leaves a gap on one side, and the leak returns.
After the repair: check the connections
Dry the cabinet floor and place a paper towel beneath the connections. Run water for a few minutes and watch the towel. If it stays dry, run the disposal and check again, because vibration reveals loose fittings.
If the sink drains slowly after the repair, the clog may be downstream. Many Pleasant Hill kitchens share a single run among the sink, dishwasher and disposal, and a grease clog affects all of them. Our drain cleaning page explains the next step.
When to call a plumber
Corroded or stuck parts
Old mounting rings can fuse to the flange and are best removed by someone with the right tools.
Cracked sink
A damaged sink bowl will not hold a seal.
Persistent leaks
If a fresh seal still weeps, something else is wrong.
Electrical concerns
Wiring problems at the disposal need a professional.
Choosing the right putty and mounting kit
Plumber's putty stays soft and seals against a stainless sink, but some natural stone and certain plastics are stained by it. If your sink is stone or acrylic, check the sink maker's advice, and use a silicone product only if the instructions call for it.
Mounting kits differ by brand. The snap ring, backup ring and mounting ring are not interchangeable across all disposals, so use the kit that came with your unit. If you only have loose parts from an older model, buy a matching kit instead of improvising, since a near fit leaks.
Keep the old parts until the new seal passes its test. If something does not line up, you can compare them instead of guessing.
Pleasant Hill: sinks, cabinets and sewer lines
Kitchens in older Pleasant Hill homes often have shallow cabinets and mixed generations of plumbing under the sink. If you see galvanized steel pipe, that is a sign the home dates from the postwar decades, when the post office opened in 1948 and the Gregory Gardens subdivision was developed in 1950.
If kitchen drain water backs up beyond the sink, the issue may be in the private sewer lateral. Central San says the owner is responsible for the lateral, and recommends inspection or cleaning at least every other year when trees stand near it.
For neighbors in other towns, the Concord page and Walnut Creek page explain how we cover them.
Local questions
Not always. A careful homeowner can do it, but a stuck mounting ring or a cracked sink calls for a professional.
Plumber's putty is the standard for the flange seal.
The flange seal has likely failed. Reseating the flange with fresh putty usually fixes it.
Putty does not need long to cure, but check for leaks after a few minutes of running water.
The clog is probably downstream, and a drain cleaning is the next step.
Still have a question about your situation? Call (855) 575-2890 any hour and describe what you are seeing.