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Replace a garbage disposal: 14 ways to avoid leaks and mistakes.

When you flip the switch to turn on the garbage disposal and all you get is a hum--or a loud, metal-on-metal grinding noise--you know something's wrong. Maybe it's just trash stuck in the disposal, but there's also a chance that the unit is dead, kaput, never to dispose again.

Fortunately, replacing a disposal isn't hard, even if you haven't done much plumbing. Manufacturers provide clear instructions that tell you most of the things you need to know--but not everything. We talked to veteran plumbers and collected their best tips for a smooth, trouble-free installation.


A disposal that seems to be dead might be revived with a simple fix. Here are three things to try:

* Look for a jam. Something too tough to grind, such as a piece of glass, could be jamming the motor. Turn off the power and water, then unplug the disposal. (If it's hardwired, turn off the breaker.) Remove the rubber baffle inside the drain-- most just lift out--and shine a flashlight into the hole. Fish out the obstruction with a pair of tongs or needle-nose pliers.

* Turn the motor manually. You'll need a hex wrench. Some disposals come with one bent at a convenient angle, but if you don't have it, you can buy one at a hardware store or use a standard Allen wrench. Rotate the wrench back and forth as shown above until the motor turns a full revolution, then remove the wrench and switch on the motor.

* Press the reset button. If your motor has overheated by working too long, wait five minutes for it to cool down, then push the reset button. (It's usually located on the underside of the disposal.) The motor may also have overheated because of a jam. If the motor doesn't start after manually turning it, try pushing the reset button.


When you buy a new disposal, the box will contain all the parts you need to install it. Before you jump into removing the old unit, take a few moments to familiarize yourself with all these parts. Put them together in the correct order and try out the locking mechanism. Understanding how everything fits together ahead of time will make the job a cinch.

Disposal system anatomy

If you have a double sink, the best way to plumb a disposal is to run its discharge tube directly to a tee below the opposite sink. The tube must drop about 1/4 in. in order to drain properly.


Everyone who's installed a few disposals is aware of this mistake: Forgetting to remove the dishwasher knockout before hanging the unit.

If you have a dishwasher, the first thing you should do after removing the disposal from the box is to punch out the knockout with a hammer and a screwdriver. Fish out the knockout by reaching down inside the disposal. You don't want this plastic disc to be the first thing that the disposal tries to grind up!

This is also the best time to add the cord and plug to your disposal. It's really awkward to add these after the disposal is installed.

Support the weight

Garbage disposals can weigh 15 lbs. or more. That's a lot of weight to suddenly catch with one hand while you're turning the lower mounting bracket with the other hand.

Before you unhook anything, assemble a support under the unit using a paint can and scraps of wood. Leave a 1/4-in. to 1/2-in. gap under the unit so it can drop a bit. Use the same support to help you install the new disposal.


Surprise! Most new disposals don't come with a cord and plug. If your old unit has a cord and plug, you can remove the whole assembly and reinstall it on the new unit. (Instructions are included with the new disposal.) Or you can simply buy a new cord and plug when you buy the disposal. They're usually located together in the store.

If you're not comfortable making electrical connections, you can buy a disposal that already has a cord attached. Ask at your home center or appliance store, or search online for "garbage disposal with cord attached."

Prepare for a new discharge tube

Your old discharge tube probably won't be the right length for your new disposal. If it's too long, simply connect it to the disposal, mark it and cut it with a hacksaw. (Loosen the other pipe connections, if necessary, to insert the tube back into the tee.) If the old discharge tube is too short, you may have to make a time-wasting trip to the store. To avoid this, make sure the new disposal includes a tube, or buy one separately at the same time for about $3.


The snap ring fits into a groove on the lower end of the sink flange. When you're working under the sink, it prevents the upper mounting bracket from falling off. Removing an old snap ring can be frustrating--unless you know this trick: Starting at the break in the ring, insert a thin-blade screwdriver between the ring and the flange. Pull down on the ring with the screwdriver's blade and walk the blade around the ring. The ring will pop right off.

Shortcut: Keep the flange

If your old sink flange is undamaged and tight, with no signs of leakage, you can probably leave it in place. Chances are good that the mounting brackets on the new unit will fit just fine. To find out, remove the old disposal and install the new flange on it. If it fits, you can install the new disposal using the old flange.

Weight down the sink flange

After you install the new sink flange, you don't want it shifting around when you're assembling the parts underneath. Movement of the flange could break the seal between the flange and the sink, inviting a leak.

Your best bet is to ask a helper to press down on the sink flange, or if you're working alone, find something to weight it down, such as the old disposal. Place an old towel under the weight so you don't scratch the sink. If the bottom of your sink is quite concave, the old disposal might not contact the flange. In that case, place a can on the flange, then weight down the can.


When you hang the new disposal, rotating the lower mounting ring tightens the seal between the disposal and the sink flange. The lower ring rides up a set of ramps on the upper ring--pretty neat! But the final inch or so of rotation requires a fair amount of force.

The easiest way to apply that force is to squeeze them together using tongue-and-groove pliers, such as Channellocks. You'll need medium or large pliers to do this. Unlike prying on the lower ring with a screwdriver or hex wrench--the method recommended in most instruction sheets--squeezing can't disturb the position of the sink flange and cause it to leak. Plus, it's easier on the wrists.

Compare outlet heights

A disposal's discharge tube must slant about 1/4 in. downhill in order for it to drain properly (see Figure A, p. 31). Creating that drop may be a small problem if the outlet on your new disposal (left) is lower than the outlet on your old one, as shown above.

To be prepared, measure the distance from the outlet to the top of each disposal before you remove the old unit. If the new unit's outlet is lower, you must also lower the tee that the discharge pipe connects to. Loosen the two nuts that connect the tee to the tailpiece above and the trap below. Try lowering the tee to see if the tailpiece is long enough. If it's not, you'll have to replace it with one that's slightly longer.

Spend a little more

You can buy a 1/3-hp disposal for $80 or less, but our experts suggest that a more expensive unit with at least 3/4 hp would be a better choice. The more powerful the motor, the less chance it will jam. In addition, higher-priced disposals are generally quieter and have longer warranties.


Plumber's putty is typically recommended for sealing the sink flange to the sink itself, but silicone will provide a more reliable seal. With silicone, there's almost no chance--now or later--that the flange will leak.

However, when it's time to replace the disposal and the sink flange again, you should know that old silicone is much harder to remove than old plumber's putty. But that's why it works better!

Inspect the plumbing first

Look over all the pipes under your sink for any sign of leakage before heading to the store to buy a new garbage disposal. You might want to replace more than just the disposal itself, so you may as well make a list and be prepared!


TIME: 2 to 3 hours

COST: $80 to $300


TOOLS: Screwdriver, putty knife, tongue-and-groove pliers, hacksaw

by Tom Caspar
COPYRIGHT 2015 Home Service Publications, Inc.
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Author:Caspar, Tom
Publication:The Family Handyman
Date:May 1, 2015
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