Garbage disposal repair — press the reset button first

Most garbage disposal calls are one of four things: it hums, it does nothing at all, it leaks, or it has simply worn out. Two of those you can often sort out yourself in ten minutes, and it is worth knowing which.

Disposals are also the fixture most often blamed for problems they did not cause. A kitchen sink that drains slowly is usually a drain problem with a disposal attached, not a disposal problem — and replacing the unit fixes nothing.

The four faults

It hums but does not turn. The motor has power but the impeller plate is jammed, and the overload will trip shortly if you leave the switch on.

Nothing at all, no sound. Power. Press the reset button on the base first, because a tripped overload is the single most common cause and looks exactly like a dead unit.

It leaks. Where it leaks tells you what it costs. At the top, where the unit meets the sink, it is the mounting flange and plumber's putty seal — a resealing job.

Poor grinding, noise, or it stalls under load. Worn impellers and grinding ring, corroded chamber, or an undersized motor being asked to do too much.

Press the red reset button. It is on the underside of the unit, it takes four seconds, and it is the answer roughly half the time somebody calls to say the disposal is dead.

When the disposal is not the problem

This is the part worth reading before buying a replacement unit.

A disposal that runs normally but leaves the sink draining slowly, or backing up, is telling you the obstruction is past it.

The signals that point downstream rather than at the appliance: the other basin of a double sink backs up when the disposal runs; water comes up in the sink when the dishwasher drains; the sink drains slowly even with the disposal switched off and the strainer clear; or other fixtures in the house are slow too. Any of those is drain cleaning territory, and where grease has built up over years, hydro jetting is what actually restores the pipe rather than punching a hole through the blockage.

One more: if the dishwasher is not draining properly, check whether the disposal's dishwasher inlet plug was ever removed. On a new installation that plug has to be knocked out before the dishwasher hose is connected, and it is a genuinely common oversight — the symptom is a dishwasher that will not drain at all from the day it was installed.

Safety, briefly but seriously

Two rules, and they are not negotiable.

Never put your hand into a disposal with the power on, and when clearing a jam, switch off at the breaker rather than trusting the wall switch. A disposal that has tripped its overload can restart when the overload cools, and a unit whose switch someone else might flick is genuinely dangerous. Turning the breaker off takes a minute.

Retrieve objects with tongs or pliers, never fingers, even with the power off — the impellers themselves are blunt but the chamber often contains glass or metal fragments.

And do not use chemical drain cleaner in a disposal or in the drain beneath it. It does not clear grease effectively, it sits in the chamber and trap where the next person to work on it will meet it, and it can damage the seals and the metal components. If a plumber arrives to find a chamber full of caustic, that is a worse job than it needed to be.

Choosing a replacement

Disposals are one of the few appliances where the cheap option is genuinely a false economy, but the most expensive one is rarely necessary either.

Motor size. A larger motor jams less and grinds more thoroughly, and for a household that uses the disposal daily it is the upgrade worth paying for. For light occasional use the smallest units are adequate. Undersized motors in heavy use is where most premature failures come from.

Continuous feed versus batch feed. Continuous feed — the wall-switch type most people have — is convenient. Batch feed requires a stopper to be in place before it runs, which makes it substantially safer around children and effectively impossible to run with cutlery in it. Worth considering rather than dismissing.

Stainless grinding components. Galvanised components corrode, particularly in hard water. Stainless steel impellers and grinding rings last considerably longer and are standard on better units.

Sound insulation. Genuinely noticeable in an open-plan kitchen, and one of the few premium features that people consistently report being glad they paid for.

Installation and the electrical question

Fitting a disposal is straightforward on a sink that already has one and more involved on a sink that does not.

The mounting flange seats in the sink opening with a putty or gasket seal and the unit hangs from a mounting ring. The discharge connects through an elbow to the trap, and here the geometry matters: the trap arm must still have proper fall to the wall connection, and on a double-bowl sink the second basin has to tie in correctly. A disposal fitted without regard to that geometry is the reason plenty of kitchen sinks drain badly after a remodel.

If a dishwasher is connected, the inlet plug is knocked out and the hose is run with a high loop or through an air gap as the local code requires, so drain water cannot siphon back into the dishwasher.

Electrically, a disposal needs a switched supply — either a dedicated switched receptacle under the sink for a corded unit, or a hardwired connection with a wall switch. Adding that where none exists is electrical work, and it needs to be done properly rather than by extending a convenience outlet. It is worth knowing up front, because it is often the largest part of the cost of adding a disposal to a sink that never had one.

Then it gets tested: run water, run the unit, check the flange seal from below, check the dishwasher drains, and check the trap connections dry after a few minutes.

What drives the price

We refer to independent contractors and cannot quote for them, but disposal work is at the predictable end of plumbing.

Clearing a jam and resetting is the smallest possible service call, and often gets folded into a visit for something else. Replacing a leaking drain elbow gasket or resealing the mounting flange is similarly modest. Replacing the unit itself is short labour plus the appliance, and the appliance is the larger share — with the note that a mid-range unit with stainless components and a decent motor is usually the right buy rather than the cheapest.

Cost grows in two situations. First, where there is no existing disposal: the sink opening may need a different flange, the trap arrangement usually needs reworking, and the switched electrical supply may need running, which is the expensive part. Second, where the reason for the call turns out to be the drain rather than the appliance — then you are into drain cleaning, and if years of grease are involved, jetting.

It is worth batching. If a plumber is coming for a faucet or a toilet anyway, adding a disposal replacement to the same visit costs far less than a separate call. Our faucet and fixture installation page covers the rest of the kitchen.

• Breaker off — not just the wall switch — before clearing any jam
• Press the reset button on the underside before assuming the motor is dead
• Retrieve jammed objects with pliers, never by hand
• No chemical drain cleaner in or below a disposal
• Cold water while grinding, and keep it running well afterwards
• A leak from the bottom of the housing means replace, not repair