The short answer: seal it, seat it, tighten from below
The sink flange needs a watertight seal against the sink bowl and a firm, even squeeze from the mounting assembly underneath. Everything else on the job, the wiring, the drain connection, the dishwasher hose, comes after that joint is right. If the flange weeps, the cabinet floor pays for it.
Plan on a slow first try. The instructions in the box matter more than any general guide, this one included, because the mounting ring design differs from brand to brand. Where this page and your manual disagree, follow the manual. Our garbage disposal team sees the leaks that follow a rushed swap.
Before you touch anything
- Switch off the disposal's circuit at the breaker panel, then flip the wall switch to confirm it is dead. A wall switch alone is not a safe way to work under a disposal.
- If the unit plugs into an outlet under the sink, unplug it. If it is hardwired, leave the wiring to someone comfortable with it, or call.
- Empty the cabinet and set a bucket and towels under the trap. Old disposals hold more water than you expect.
- Lay out the flange, fiber gasket, backup ring, mounting ring, snap ring and screws from your kit, plus plumber's putty if the instructions call for it.
- Look at the sink rim. A cracked or chipped opening is a reason to stop and ask someone to look.
Plumber's putty or gasket? What each seal does
Many kits use both: putty at the sink bowl and a gasket further down the stack. Your manual decides which goes where.
| Seal | Where it goes | Good to know |
|---|---|---|
| Plumber's putty | Rolled into a rope and pressed under the lip of the sink flange | Stays soft and fills small gaps. Some sink materials, such as natural stone, can be stained by it, so read the putty label and your sink maker's guidance. |
| Rubber or fiber gasket | Between the flange and the mounting assembly under the sink | Part of most kits. Keep it flat and centered when you stack the parts, since a pinched gasket leaks. |
| Silicone sealant | Specified instead of putty by some kits and sink makers | Cures instead of staying soft, so follow the tube's cure time. |
If your instructions name a specific sealant, use that one.
Installing the flange, in order
Remove the old unit
With power off and the bucket in place, release the old disposal from its mounting ring, disconnect the drain and dishwasher hose, and lower it out. Then loosen the old ring and push the old flange up through the sink.
Clean the opening
Scrape off old putty with a plastic scraper so you do not scratch the sink. Wipe the opening dry, because putty and sealant stick poorly to a wet or soapy surface.
Seat the new flange
Roll a rope of putty about as thick as a pencil, press it under the flange lip, and drop the flange into the opening. Press down firmly and hold it, since the seal comes from weight and squeeze together.
Build the assembly from below
Slide on the gasket, backup ring, mounting ring and snap ring in the order your manual shows. Tighten the three screws a little at a time in rotation, like lug nuts, until putty squeezes out evenly, then wipe it away.
The dishwasher knockout people forget
If a dishwasher drains into the disposal, the new unit has a small plug inside its dishwasher inlet. That thin disc has to be knocked out before the dishwasher hose goes on. Tap it out with a screwdriver and a light hammer, then fish the loose disc out of the grinding chamber with pliers.
Skip it and the dishwasher sits full of water after every cycle. If no dishwasher drains into this disposal, leave the plug in place.
Hang the unit and test for leaks
Lift the disposal onto the mounting ring and turn it until it locks. Reconnect the drain elbow with its gasket, then the trap, and clamp the dishwasher hose back on. Hand tighten first, then snug, and do not crank anything.
Restore power only when everything is assembled. Fill the sink with a few inches of water, let it drain, and check the flange, elbow and trap with a dry paper towel. A weep at the flange usually means the screws need another even turn or the putty went onto a wet surface.
A drip that looks like the flange can come from the faucet base above it, which is faucet repair territory. A first disposal where none existed needs power and drain changes that count as plumbing installation.
Allendale, MI: sewer, septic and rental kitchens
Much of Allendale Township is served by the township's own sewer system, which includes its Water Resource Recovery Facility, about 50 miles of sewer main and 8 lift stations. Areas without municipal service rely on private wells and septic systems, and the Ottawa County Health Department oversees those. If you are on septic, ask the county health department whether a disposal suits your system before you buy one. We cannot make that call for you.
Allendale also has a lot of rental housing. Census Bureau estimates for 2020 to 2024 put about 47 percent of households in the Allendale CDP as renters, and the township's Master Plan counts 17.5 percent of residents in group quarters such as dorms. If you rent, the disposal usually belongs to the landlord, so ask before you swap one and report a flange leak right away.
Source: the township's water and sewer page, its Master Plan, and Census Bureau ACS estimates for 2020 to 2024.
Do it yourself, or call a plumber?
A like-for-like swap is a fair weekend job.
Reasonable to do yourself
- Swapping a plug-in unit for a similar one
- A sink in good shape with an opening that matches the flange
- A kit with clear instructions and an afternoon to spare
Better to call us
- A hardwired unit with no clear cable or switch
- A cracked sink rim, a stone counter, or a flange that keeps weeping
- A first disposal in a kitchen that never had one, which needs power, a switch and often a trap change
Flange leaking or not sure what you are looking at?
Call us any hour and describe what you see. We will tell you what is likely wrong and give you the clear price before work starts.
Call (855) 575-2890