Solved! What should I do if my garbage disposal leaks?

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Suspect a leak in one of your kitchen’s top appliances? Identify the problem and repair a leaking garbage disposal with these tips and techniques.

Q: Recently, the cabinet under my kitchen sink has become mysteriously soggy. Could this be a symptom of a leaking garbage disposal? If so, how can I fix it myself?

A: A leaking garbage disposal often goes unnoticed until you are confronted with a soggy piece of furniture, a smelly puddle or an audible drip from the unit. Repairing it can also be frustrating, as the leak can come from multiple components in the system. Fortunately, with a little insight, you can locate the leak and, based on its exact location, stop the seepage and repair the component that caused it. In the worst case scenario, if it turns out that the disposer needs to be replaced, installing a new disposer is a reasonable do-it-yourself task for those with basic plumbing knowledge. Read on to save money that you would have had to leave to a professional.

Be prepared to find the leak.
Before testing the garbage disposal for leaks, unplug it from the wall outlet and turn off the power to the breaker box to avoid electrical shock. Then insert a leak-proof plug into your sink drain and wipe the unit down with a clean cloth. In a handy container, mix a few drops of food coloring in a few cups of water, and pour the colored water over the sink plug to help you locate the leak.

Look for the source.
Using a flashlight, examine the unit to see if colored water is leaking, which is likely to come from one of three places:

the top, where the disposer meets the sink drain
the side, where the dishwasher hose or main drain connects to the disposer
or the bottom of the unit.
Inspect each of these areas by running a light-colored cloth over the unit; colored water will easily show on the cloth and reveal the location of the leak. If the leak is not immediately apparent, remove the sink plug and pour a few more cups of colored water down the sink drain, then check again for leaks. Leaks near the top of the unit are more likely to show up when the sink is clogged, while side and bottom leaks are more visible when the sink is unplugged.

If the top of the garbage disposal is leaking, re-seal and tighten the flange.

The metal sink flange that sits directly inside the sink drain is typically sealed around the top with plumber’s putty (a clay-like sealant) and then secured from under the sink with bolts. If the plumber’s putty deteriorates, or the bolts loosen, the flange can no longer form a watertight seal between the sink drain and the disposal—which could cause a leak at the top of the unit.

To reseal the leaky flange, you must first detach the garbage disposal. Start by loosening the screws securing the main drain pipe to the disposal, then loosen the screws in the metal clamp securing the dishwasher hose to the disposal and detach the drain pipe and dishwasher hose from the disposal. Loosen the screws in the mounting ring that connects the disposal to the metal mounting assembly beneath the sink, then pull down the disposal and carefully set it on a clean, dry surface. Loosen the bolts in the mounting assembly with a wrench, then pull down the mounting assembly and set it near the disposal.

Lift the sink flange from the top of the sink. Use a plastic putty knife to scrape off the old plumber’s putty around the top of the flange, then wipe off any putty residue with a damp rag. Now grab a palmful of plumber’s putty (available at hardware stores, home centers, and online) and roll it into an eighth-inch to quarter-inch-wide “rope” with a length roughly equal to the circumference of the flange. Wrap the rope of putty around the top of the flange like a collar, then insert the flange into the sink drain opening until snug. Re-install the mounting assembly and mounting ring (taking care to securely tighten the mounting bolts on the mounting assembly), then re-attach the garbage disposal, drain pipe, and dishwasher hose in the reverse order you detached them.

If you see that it’s the side of the garbage disposal leaking, tighten drain line connections and replace worn gaskets.

Two drain lines extend from the sides of a garbage disposal: a narrower dishwasher hose that connects the dishwasher drain pipe to your disposal’s dishwasher inlet, and the main drain pipe that connects your disposal to the sewer through an outlet in the wall.

If you spy a leak on the side of the disposal where the dishwasher hose meets the disposal’s dishwasher inlet, the problem could be that the metal clamp connecting them is loose. In that case, tighten the screws in the metal clamp with a screwdriver.

If the leak is on the side where the disposal meets the waste drain pipe, loosen the screws that secure the drain pipe to the disposal and inspect the rubber gasket inside the pipe—it may well be worn out. Replace the gasket and re-tighten the drain pipe screws.

If the bottom of the unit is leaking, replace the disposal.

Leaks from the bottom of the garbage disposal (often from the reset button) commonly indicate that at least one seal on the interior shell of the unit that protects the motor has deteriorated, or that the shell itself has cracked. These vulnerabilities can cause water from the sink to seep into the shell of the disposal and leak out of the base of the unit. In an old garbage disposal, one compromised internal seal is often accompanied by others, so your best bet is to install a new one.

Calling in a professional to replace the unit will cost you an average of $400, including labor and parts, or you can install a garbage disposal yourself and save between $90 and $200 in labor costs. You should be able to use a new disposer for 8 to 15 years.

Check your work by running water down the drain.
Whether you repaired or replaced the leaking garbage disposal, check for any missing problem areas. Wipe down the unit with a clean cloth, then unplug the sink drain (if it is clogged) and pour a few cups of colored water down the drain again. Use a flashlight to inspect the entire unit. If you do not see a leak, turn on the disposer from your breaker box and plug the disposer into the wall outlet.

Prevent future leaks.
Proper use of a garbage disposal can prevent future leaks. Remember to grind only soft foods; hard items such as bones, apple cores or raw potatoes can dislodge or damage internal seals. Run cold water down the sink drain before and after food disposal to prevent solid grease from clumping (which can damage the sink flange and cause leaks). Finally, check your disposer for leaks at least twice a year using the colored water test to detect and repair small leaks before they damage sink cabinets or the kitchen floor.