A leaking garbage disposal shows its cause by where the water appears. Top leaks mean a loose mounting or flange seal. Side leaks at the dishwasher inlet often mean a missing knockout plug or loose clamp. Discharge leaks mean a loose bolt or bad gasket. Water from the body or bottom usually means replacing the disposal.
Where is the water coming from?
InSinkErator's troubleshooting guide breaks a leak into six spots. Use it as a map and match what you see.
| Where the water shows | What it usually means | What to do |
|---|---|---|
| Top of the disposal, at the sink flange or mounting assembly | The mounting is loose, or the flange seal is not tight | Fix the mounting |
| The discharge pipe on the side | A loose nut or bolts, a worn gasket or a cracked elbow | Tighten or replace the parts |
| The dishwasher inlet | A missing knockout plug, a loose clamp or hose adapter | Check each one |
| The bottom, the body wall or the motor joint | A failure inside the unit, once you have ruled out the top | Contact the maker, and expect to replace it |
| A pipe next to the disposal | A loose joint in the plumbing around it | Tighten the joints or call a plumber |
Two cautions come straight from InSinkErator. If water appears at the bottom or through the body wall, confirm that it is not really coming from the top and dripping down the outside. Water runs along metal and can travel a long way before it drips. A wet bottom is often a top leak in disguise.
How do you find a leak that's hard to see?
A slow drip is hard to trace with a flashlight. InSinkErator gives a method that works for any brand.
- 1Empty the cabinet under the sink.
- 2Lay a sheet of newspaper flat across the bottom of the cabinet and tape it down. If water drips from a leaking spot, it leaves a wet mark on the paper.
- 3Put the stoppers in the sink and fill it with water. Leave it full for a while, then look for leaks.
- 4Pull the stoppers and let the sink drain. Look again.
- 5Turn on the water and the disposal and let them run while you watch for drips.
If you find nothing, leave the paper in place for a few days. If the paper stays dry, the water may be coming from somewhere else, and InSinkErator lists what to check: the water filters, the dish sprayer, the faucet, the dishwasher drain hose, the seam between the sink and the countertop, and the countertop joints. See how plumbers find hidden leaks for what to do when the source is inside a wall.
How do you fix a leak at each spot?
The fix depends on the location. Work from the top down.
### What fixes a leak at the top?
A leak at the top is a leak at the sink flange or the mounting assembly. The flange is the metal ring that sits in the drain opening, and the disposal hangs from it on a set of mounting rings.
Waste King's installation instructions describe a simple test of the flange seal. After you tighten the support ring onto the flange by hand, you can put the stopper in the sink and fill it with water to check the flange seal and make sure there are no leaks. You can repeat that check on an installed unit. If water seeps under the flange when the sink is full and the disposal is dry, the flange seal is the problem. Fixing it usually means loosening the mounting, cleaning the seal surface and reseating the parts, which is where many homeowners call a plumber.
Moen's limited warranty helps explain why top leaks are so common after a bad install. It says the warranty does not cover damage from incorrect installation or mounting, "such as electrical connections due to improper installation, leaks at the sink flange, dishwasher inlet or discharge elbow, or damage from excessive torqueing of manufacturer's screws." In other words, the maker treats those three leak spots as installation problems, not product defects. That's useful to know if your disposal is new and leaking at one of them.
### What fixes a leak at the discharge pipe?
Water at the elbow where the disposal drains into the trap points to the discharge connection. InSinkErator's steps are short:
- Check that the discharge nut or bolts are tight.
- Check the gasket for debris, cracks or rips, and replace anything cracked.
- Look at the discharge elbow for cracks, and make sure the elbow-to-trap joint is tight.
- On Evolution models, confirm the discharge tube is seated in the anti-vibration tailpipe mount and secured with the original spring-load hose clamp, and check that mount for cracks or damage.
- If water comes right out of the discharge opening, check whether the detergent shield is buckled.
Don't crank the fasteners as hard as you can. Waste King's installation sheet says "DO NOT OVER TIGHTEN" at the discharge elbow, and Moen's warranty text lists damage from excessive torque as an installation fault. Waste King also says not to reuse the old discharge elbow and gasket, because the old gasket may not seal properly. If you swap a unit, use the new elbow, gasket, flange and screws that come in the box.
### What fixes a leak at the dishwasher inlet?
If your dishwasher drains through the disposal, its hose connects at the small inlet on the side of the unit. This spot leaks for a few simple reasons. InSinkErator says to check these, and its guide applies only when a dishwasher drain hose is attached to that inlet:
- 1The knockout plug. The inlet ships blocked by a small plug inside the disposal. It has to be knocked out before the dishwasher hose can drain through it. If the plug is still in, dishwasher water has nowhere to go.
- 2The clamps. Check that they are tight.
- 3The hose adapter. If you use one, make sure it is intact and tight.
- 4The elbow and trap joint. Verify that this joint is tight.
Waste King's troubleshooting section adds a warning that goes with item one. Odd noises are often caused by a foreign object, and it lists "dishwasher knockout plug" along with a spoon or a bottle cap. A plug that was knocked into the chamber and never fished out can jam the disposal. Turn off the switch and the water, take the object out and never put your hands inside.
If the water is coming from the dishwasher side instead, see why a dishwasher leaks for the door, supply and drain checks.
When does a leak mean the disposal has to be replaced?
Three spots usually end the repair discussion: the bottom, the container body and the motor joint. InSinkErator tells you to confirm the water is not coming from higher up, and if it is really from the wall of the container or the motor joint, to contact the manufacturer. InSinkErator sends you to the manufacturer for these, not to a list of parts to swap, which tells you they are not a home repair. A disposal with a body leak or a motor-joint leak is usually a replacement.
Replacement is also the safer choice if the unit is old and leaking near the motor, since water and electric power sit close together. Unplug it or turn off the breaker before you reach into the cabinet.
### What should you do right now?
- Turn the disposal off. Use the switch, and unplug it or turn off its breaker if water is near the cord or the motor.
- Stop using that sink if water is pouring out, and put a bucket under the leak.
- Dry the cabinet. Wet particleboard swells and can grow mold, so get the base and sides dry.
- Photograph the damage if the leak reached the cabinet or the floor, since you may need it for a water damage insurance claim.
- Check the reset button after any repair. If the disposal was wet and stopped, see where the reset button is.
If the water is coming fast, treat it as an emergency plumber call. HQ is licensed and insured, offers 24/7 emergency service, and gives free estimates and upfront pricing on disposal repair and replacement.
If the leak is at the body or the motor joint, the unit is likely at the end of its life, and how to replace a garbage disposal walks through the swap. To head off the next leak, see how to maintain a garbage disposal so it lasts.