Installing a Garbage Disposal

Although not the most glamorous kitchen improvement, the addition of a garbage disposal will be greatly appreciated by the chef of the house.

Because disposals vary greatly in size and bowl depth, check the dimensions to make sure the disposal you've chosen will fit under your sink.

Since installing a disposal requires both plumbing and electrical skills, it's a project best taken on by experienced do-it-yourselfers. One way to simplify the task is to have a licensed electrician install a GFCI (ground fault circuit interrupter) outlet under the sink and a separate wall switch adjacent to the sink--then the only electrical work left is to wire a power cord to the disposal.

Always shut off the power to the circuit that will serve the disposal before beginning any work. If you're replacing a disposal, turn off the electricity to that circuit and unplug the disposal or disconnect the wiring before removing the unit.

First, disconnect and remove the existing waste assembly, from the sink flange to the trap. Have towels and a bucket handy to catch water and debris. Once the waste lines are out of the way, remove the mounting assembly from the disposal and install the new flange in the sinkhole, applying a coil of plumber's putty around it before dropping it into place, as shown.

Finally, connect the disposal to power. Either run a line or have a licensed electrician run power into the sink cabinet and install a GFCI receptacle. If your disposal didn't come with a plug on the end of the cord, wire the recommended grounded electrical cord to the disposal. Plug into the receptacle.

Rotate the disposal so that the discharge tube aligns with the drain trap. If your sink is a double-bowl model, you'll need to re-plumb the waste line to attach to the disposal. If you're lucky, all you'll need is an extension tube. If not, you may need to replace the entire assembly, shown here.

Position the disposal under the mounting assembly so that the mounting tabs can slide over the mounting tracks. Lift the disposal and insert the top into the mounting assembly. Rotate the lower mounting ring until all three mounting tabs lock over ridges in the mounting ring. Use the wrench provided or a screwdriver to tighten the ring.

To get ready to attach the disposal to the mounting assembly, first attach the discharge tube, as shown. Then, inspect the P-trap and clean out any hardened waste. Next, prepare the dishwasher drain connection. This usually entails knocking out a drain plug from the dishwasher nipple and attaching the drain hose from the dishwasher.

Attach the upper mounting assembly to the sink flange, placing a heavy object such as a large phone book on top of the flange to hold it in place. Follow the manufacturer's directions for gasket placement and slip the mounting ring over the flange. Then, slide the snap ring onto the flange until it pops into the groove on the flange. Next, tighten the three mounting screws, as shown, until the assembly has a tight seal against the sink.