Parts and tools checklist
Gather everything before you shut off the water, because a half-finished install leaves the sink unusable.
- The disposal unit, sized to your household and motor strength.
- Mounting kit with flange, gasket, backup ring and snap ring.
- Plumber's putty for the sink flange.
- Dishwasher drain knockout plug removed if a dishwasher connects.
- Power cord kit or a wired connection, depending on the unit.
- Discharge elbow and a new trap arm gasket.
- Screwdrivers, adjustable pliers, a hammer and a bucket.
Check the box before you start. Some disposals ship without a power cord, so the kit needs to match how your outlet is set up. Others include everything but putty.
Picking the right size and type
| Type | Best for | Trade-off |
|---|---|---|
| Continuous feed, 1/3 to 1/2 horsepower | Small households, light use | May jam on tougher scraps |
| Continuous feed, 3/4 to 1 horsepower | Families, frequent cooking | Costs more, runs louder without insulation |
| Batch feed | Homes with young children | Needs the lid in place to run, slower to use |
Most households do fine with a mid-range motor. Pay for sound insulation if the kitchen is open to a living area. A stainless steel grinding chamber lasts longer than a galvanized one.
Installation steps
- Kill the power. Switch off the breaker for the sink outlet and unplug or disconnect the old unit. Check that the circuit is dead before touching wires.
- Remove the old disposal or sink strainer. Unscrew the discharge pipe, twist the unit off its mounting ring and clean the sink opening of old putty.
- Mount the new flange. Roll a rope of plumber's putty under the flange, seat it in the sink and attach the mounting assembly from below.
- Connect the electrical. Follow the instructions. Use a cord and plug or a wired connection to the junction box, with the ground wire attached.
- Hang the disposal and align the drain. Lift it onto the mounting ring, lock it, then connect the discharge to the trap arm with a new gasket.
- Test for leaks. Fill the sink, drain it, then run the disposal with cold water and look at every joint with a dry paper towel.
What it costs if you hire it out
National cost guides put a new disposal installation at roughly $250 to $650 and a replacement at $200 to $550. A repair runs $100 to $250. A common rule is to replace when the repair costs more than half of a new unit, or when the disposal is older than 8 years.
These are national figures, not a local quote. We give a clear price before work starts.
A failed disposal is often cheaper to replace than diagnose when the motor hums and does not turn.
Hazelwood notes for disposal installs
Plumbing work in Hazelwood needs a St. Louis County license, and plumbing permits and inspections are handled by the county through the city. A simple like-for-like swap often needs no permit, but a new drain or wiring change can, so call Inspections and Permits at 314-513-5034 if you are unsure. A neighboring city's code, Florissant's, lets owners of detached single-family homes pull their own plumbing permit for their own work, but check what applies in Hazelwood before assuming it does.
The sewer here is run by the Metropolitan St. Louis Sewer District, and grease sent down a disposal still ends up in the line. A disposal grinds food, but it does not make grease safe to pour out. Scrape fats into the trash, since they harden in the lateral and lead to clogs.
Disposals are listed to UL 430, and the International Plumbing Code (IPC) requires a trap and vent on the sink drain. Read the unit's instructions before you start, and remember the dishwasher knockout plug.
When to call a plumber
A swap of one disposal for another is a reasonable project for a patient owner. A first-time install is harder, because it may need a new outlet, a switch, a drain repiped to the trap, and a dishwasher hookup. Wiring mistakes are a shock and fire risk.
Call a licensed plumber when the sink drain does not line up, when there is no power under the sink, when old pipes crumble as you loosen them, or when a leak shows up after you reassemble. Our garbage disposal repair and installation service covers the whole job. If the kitchen sink also drains slowly, drain cleaning clears the branch before the new disposal goes in.
If the faucet is old and leaking while you have the cabinet open, faucet repair fits well at the same visit. We also serve Florissant and Maryland Heights homeowners with the same kitchen projects.
We do not run new electrical circuits. If the sink has no switch or outlet, an electrician has to supply power first.
Frequently asked questions
The disposal, a mounting kit, plumber's putty, a power cord or wired connection, a discharge gasket and basic hand tools. A drain trap that lines up with the outlet is also required.
Not if a switched outlet already exists under the sink. If there is no power source, an electrician should add one.
A replacement often takes one to two hours. A first-time install takes longer because of wiring and drain changes.
Yes. Remove the knockout plug inside the inlet if the dishwasher drains through it, and use a high loop or air gap to keep wastewater out of the dishwasher.
Plumbing permits in Hazelwood are handled by St. Louis County through the city. A like-for-like swap is simple, but call 314-513-5034 to confirm what applies to your job.
A common cause is a loose mounting ring or flange seal, or a worn gasket at the drain. Tighten the ring, reseat the gasket and check the putty seal.
Questions about your situation? A licensed plumber is on the line any hour.
Call (855) 575-2890