Answered 24/7 · repair, replace or rethink
Garbage disposals, and what they do to an older drain line
The unit, the drain it discharges into and the age of the pipe beyond it are assessed together, because a working disposal on a failing cast iron line is a problem rather than a solution.
- CFC1433655Florida plumbing contractor license
- Unit and lineassessed together, not separately
My disposal hums but does not turn. Is it dead?
Usually not. A hum means the motor is receiving power and something is stopping the plate from turning, which is a jam rather than a failure. Most units have a reset button underneath and a hex fitting in the base that frees the plate by hand. Silence with no hum is the other case: power, a switch or a failed motor.
The more useful question in this region is what the disposal is discharging into. In a South Florida house built before about 1975 the drain line is cast iron, and its bore is already rough and scaled from the inside. Ground food waste and the grease that comes with it is exactly what a rough wall catches.
So on an older line, a disposal is not a neutral appliance. It is a machine that increases the load on the pipe least able to carry it, and that is worth knowing before replacing one and expecting the drain problem to improve.
What you are seeing
What each symptom means
Two of these are the unit and three of them are not.
It hums but does not turn
Jammed. The reset button and the hex fitting underneath free most of them, and the unit is generally fine afterwards.
Nothing at all when switched on
Power, switch or motor. The reset is still worth pressing first, because it trips on overload and stays tripped.
Water under the sink when it runs
The flange at the sink, the discharge tube or the dishwasher connection. It is a leak at a joint far more often than a cracked body.
The sink backs up when it is used
The line beyond it, not the unit. A disposal cannot push waste through a pipe that has lost its diameter.
It has got noticeably louder
Worn bearings or something that has been in there a while. Both are worth looking at before the motor takes the decision out of your hands.
Questions
Straight answers before you call
Is it worth having a disposal in an older house?
It is a fair question here rather than a rhetorical one. On a cast iron drain that has already scaled, ground waste and grease are exactly what the rough wall catches, so a disposal adds load to the weakest part of the system. We would rather say that than replace one and watch you call about the drain in six months.
What should never go down one?
Grease above everything, because it coats the line rather than passing through it. Fibrous waste, bones and coffee grounds are the other usual culprits, and in this region grease is the one that turns into a recurring drain bill.
Can a jammed unit be freed without a plumber?
Often, yes. Cut the power, press the reset on the underside, and use the hex fitting in the base to turn the plate by hand. If it frees and runs normally, the job is done and you have not paid anybody.
Repair or replace?
Jams and leaking connections are repairs. A failed motor or worn bearings usually mean replacement, because the unit is an appliance rather than a serviceable assembly. That is a straightforward call and you get it plainly.
Related work
What a disposal call sits next to
Three of the five symptoms above are drain problems.
Live dispatch · 24 / 7 / 365
Humming, leaking or backing up?
A person answers at any hour. If it is backing up rather than failing, the unit is not the problem and we will say so.
No obligation. Work performed under Florida plumbing contractor license CFC1433655.