Garbage Disposal Leaking? 5 Leak Points, Found in 10 Minutes

You open the cabinet under the sink and the floor is wet. A disposal has five places water can get out, and ten minutes finds which one.

One question does most of the sorting: when does the water show up? Standing full with nothing running points at the top flange. Only while something drains points at the discharge tube or the dishwasher hose. Only while the disposal runs, and out of the bottom of the can, points at the shaft seal, which is the one branch that ends in a new unit.

Five Checks Before You Buy a Part

1. 1Unplug the disposal, or switch off its breaker if it is hardwired, before a hand goes into the cabinet. The leak has been running down onto the cord and the switch wiring. If water has already reached the junction box or an outlet, stop here and call a licensed electrician.
2. 2Dry the disposal body, both side connections and the cabinet floor, then lay a paper towel flat underneath.
3. 3Before you run any water at all, wipe the bottom of the can and the seam around the red reset button. If the towel comes up wet down there, stop here: that is the shaft seal, and more water only pushes through a leaking motor housing. Go to section 4.
4. 4Drop food coloring in the sink, fill it two inches, and wait five minutes. Color on the towel means the top flange.
5. 5Pull the sink plug and watch the discharge tube and the P-trap as the sink empties.
6. 6Start the dishwasher, hands and face clear of the hose, and watch it while the drain purge fires in the first minute.

1. Sink Flange Leaking at the Top (Most Common)

The disposal hangs from a flange sealed into the sink opening with plumber's putty. The putty dries and cracks, and water then runs down the outside of the can.

1. 1Unplug the disposal, or switch off the breaker if it is hardwired, first. Then undo the discharge tube at the side and pull the dishwasher hose off its nipple: the unit will not twist off its ring with either still attached. Put a bucket underneath.
2. 2Take the weight before the mount lets go. A half horsepower unit is 13 to 20 pounds of cast metal and a one horsepower unit up to 25, and it drops without warning into the cabinet your hands and head are inside. One hand under it, or a block of wood set on the cabinet floor to catch it, then twist it off the ring with the wrench from the box.
3. 3Most units use a three bolt mount. Back the three screws off first: while tight they clamp the stack against the snap ring and it will not budge. With the load off, pry the snap ring out of its groove with a flat screwdriver and the flange lifts out from above. Twist lock brands have no screws.
4. 4Scrape every trace of old putty off the sink and the flange. Any crumb holds the seal open.
5. 5Roll fresh putty into a rope, ring the underside of the flange and press until it squeezes out all round. On a plastic flange use the maker's foam or rubber gasket instead, because putty attacks some plastics.
6. 6Refit the snap ring, then bring the screws down a little at a time in rotation, like lug nuts.
7. 7Hang the unit back on the mounting ring and lock it, reconnect the discharge tube square to the port, and put the dishwasher hose back on its nipple with the clamp tight. The grind chamber has to be closed at the top and the port before any power comes near it.
8. 8Only now, with the unit hung, the tube on and both hands out of the sink and the cabinet, plug it back in. Fill the sink and check the flange for weeping before you call it done.

2. Dishwasher Drain Hose at the Side Inlet

The corrugated dishwasher hose clamps onto a nipple high on the side of the disposal and only carries water while the dishwasher drains. If the disposal stays dry through a full cycle, you are chasing a dishwasher leaking from the bottom.

1. 1Unplug the disposal, or switch off its breaker if it is hardwired, then start the dishwasher and get a flashlight on the nipple while it pumps out. Hands and light clear of the hose, the clamp and any wiring: the dishwasher drain pump stays live for the whole purge. It runs about 60 seconds, so be in position first.
2. 2Cancel the cycle before a hand goes in. The dishwasher pump and its wiring stay live until you do.
3. 3Tighten the worm clamp with a quarter inch nut driver until the hose no longer twists. Cranking past that cracks the nipple.
4. 4If the hose end is split or hardened, cut an inch off and clamp onto fresh material.
5. 5Check the hose loops up to the underside of the counter, or disposal water siphons back into it. Plug the disposal back in last, hands out of the cabinet.

3. Discharge Tube Gasket and Trap Joints

The discharge tube bolts to the side of the disposal against a black rubber gasket, then runs to the P-trap. Three joints in ten inches, all leak candidates.

1. 1Unplug the disposal, or switch off its breaker if it is hardwired, before you undo anything. With the discharge tube off, the grind chamber is open at the port, and a wall switch flipped by someone else puts it in motion while your hands are on it.
2. 2Fill the sink, pull the sink plug and hold a dry paper towel under each joint as it drains.
3. 3If the leak is at the disposal, undo the two flange bolts and check the rubber gasket for cracks or a curled edge.
4. 4Replace the gasket rather than reusing it. It is a $3 part.
5. 5Refit the tube square to the port and bring both bolts down evenly. Uneven tightening seals one side only.
6. 6The plastic slip nuts on the trap go hand tight only; pliers crack the nut or distort the washer. Restore power only once the cabinet is clear.

4. Water Coming Out of the Bottom of the Can

There is no gasket down there. The bottom of the housing is where the motor shaft enters the grind chamber, sealed by a shaft seal that ages out.

1. 1Unplug the disposal, or switch off the breaker if it is hardwired, before you touch it. Water inside the housing is sitting on a live connection.
2. 2Dry the can, then wipe a paper towel along the seam between the housing halves and around the reset button.
3. 3If that towel comes up wet while the flange above is dry, the shaft seal has failed. Leave the power off and stop running the sink.
4. 4Check the age before you buy anything. The shaft seal is not a serviceable part, so there is no repair at any age, but most disposals carry a two to ten year warranty depending on the model. Inside that window, the maker replaces it, and the call you make is to them, not to the hardware store.
5. 5Out of warranty, a straight swap is $80 to $150 for the unit and about an hour if the mounting ring stays put. A plumber charges $150 to $400 in labor on top of the price of the unit.

5. Loose Mounting Ring or a Torn Splash Baffle

Weight and vibration back the mounting ring screws out, and a sagging unit tips the flange seal open. A torn rubber splash baffle sprays water past the rim onto the counter while the unit grinds.

1. 1Unplug the disposal, or switch off its breaker if it is hardwired, before you touch it. Pulling the baffle leaves the mouth of the grind chamber open, and someone flipping the wall switch while your fingers are in there is how people lose them. Leave the power off until the baffle is back in.
2. 2Support the disposal with one hand and try to rock it. Any movement means the ring screws have backed off.
3. 3Tighten the screws in rotation, half a turn each, until it sits solid. Running one all the way down cocks the flange.
4. 4Check the mounting ring for a worn groove; it will not hold pressure. A full flange kit is $15 to $25.
5. 5Pull the rubber baffle out of the sink opening; on most models it lifts straight out.
6. 6Replace it if it is stiff, split or curled. It is a $6 part. Fit the new one before you restore power, hand clear of the opening.