How to Install a Garbage Disposal

Choosing the Right Disposal

Garbage disposals are rated by horsepower — 1/3 HP models handle light use for one or two people, 1/2 HP is adequate for most households, and 3/4 HP or higher handles heavy use and fibrous foods without jamming. Choose a model with stainless steel grinding components (rather than galvanized steel) for durability. Continuous-feed models run while food is inserted; batch-feed models require a stopper to activate, which is safer for homes with children. Ensure your sink has a standard 3-1/2 inch drain opening — most sinks do.

Electrical Requirements

Garbage disposals require a dedicated 15- or 20-amp electrical circuit. If you are replacing an existing disposal, the wiring is already in place. For a new installation, you may need an electrician to run a dedicated circuit. The disposal can be hard-wired or plugged into a switched outlet under the sink. Install a wall switch in a convenient location — typically next to the sink. Some disposals include a wireless switch that mounts on the wall without wiring, using a battery-powered transmitter to control a receiver on the disposal.

Mounting the Disposal

Remove the existing sink strainer by unscrewing the locknut from beneath. Clean the sink opening thoroughly. Apply plumber's putty under the new disposal flange and press it into the sink opening from above. From below, install the fiber gasket, mounting ring, snap ring, and support ring that came with the disposal unit. Tighten the mounting screws evenly until the flange is firmly seated against the sink. Wipe away excess putty from above. Hang the disposal on the mounting ring by aligning and twisting until it locks into place.

Plumbing and Testing

Connect the discharge tube from the disposal to the drain pipe using a slip-joint connection with a P-trap. If you have a dishwasher, knock out the dishwasher inlet plug inside the disposal (use a screwdriver and hammer from inside the disposal opening) and connect the dishwasher drain hose. Make all electrical connections according to the manufacturer's wiring diagram. Turn on the water, then turn on the disposal and check for leaks at all connections. Test with small amounts of food waste, running plenty of cold water. Always run cold water (not hot) when operating the disposal — cold water solidifies grease so it is chopped up rather than coating the pipes.