How do I look after a waste disposal unit?

Cold water, the right things down it, the wrong things kept out, and the small monthly routine that stops it smelling and stops it jamming.

Difficulty: beginner
Time: 15 min
Read: 6 min
Safety: caution

Short answer

Run cold water before, during and for half a minute after grinding. Feed waste in gradually rather than filling it and switching on. Keep fibrous vegetables, starchy scraps, bones, stones, fat, coffee grounds and anything non-food out. Grind ice cubes and a citrus peel monthly to clean the ring and the smell, and use it at least a few times a week even if you have little to put in it.

A waste disposal unit lasts a long time if it is used the way it is designed to be and fails early if it is treated as a bin with a motor. The failures are predictable: fibrous material wrapping the lugs, starch turning to a paste that sets in the outlet, fat cooling in the waste pipe beyond the unit, and hard objects wedging the flywheel. Almost all of them are habits rather than faults, which is why looking after one is mostly a list of what goes in it.

Safety

Never put a hand into the chamber, even when the unit is switched off — the grind ring is sharp and the flywheel can turn. Isolate at the switched fused spur and unplug the unit before anything goes near the opening. Never use chemical drain unblocker in a disposal unit; it attacks the metal and seals and can be splashed back out. Keep the plug in or a strainer fitted when the unit is not in use so nothing is dropped in by accident.

What you'll need

Cold running water
Ice cubes and a lemon or orange peel, for the monthly clean (optional)
A sink strainer or the plug, when not in use (optional)

Step by step

Run cold water before, during and after every use.Start the water, then the unit, feed the waste in, and keep both running for twenty to thirty seconds after the grinding noise clears. Cold, always, so fats stay solid and are carried away rather than melting and re-setting in the waste pipe.
Feed waste in gradually rather than loading it up.A chamber packed full before switching on is how jams start. Small amounts, continuously, with water running, is what the machine is designed for and it grinds far finer that way too.
Keep the fibrous things out.Celery, artichoke, corn husks, onion skins, asparagus, rhubarb and banana peel. Long fibres wrap round the lugs and the shaft instead of being cut, and they are what most often stops a unit turning.
Keep the starchy and expanding things out.Potato peelings in quantity, rice, pasta, oats and bread. They form a paste that sets in the outlet and the trap, and they keep absorbing water and swelling after they have left the unit.
Keep fat, oil, coffee grounds and eggshells out.Fat and oil cool and coat the pipe past the unit. Coffee grounds and eggshell membranes accumulate into a dense sludge in the trap. None of these is a grinding problem and all of them are a drainage one.
Keep hard and non-food items out entirely.Bones, fruit stones, shells, glass, metal, bottle caps, cutlery, plastic, cigarette ends, and the little bits that fall off packaging. These are what jams a unit outright. Keeping the plug in or a strainer fitted when it is not in use prevents most of them going in by accident.
Use it regularly, even with little to grind.A unit left unused for weeks develops corrosion on the ring and a stale smell in the chamber. Running it briefly with cold water a few times a week keeps everything moving and is genuinely part of its maintenance.
Clean it monthly with ice and citrus.A tray of ice cubes ground with cold water knocks residue off the lugs and the ring and sharpens nothing but does scour effectively. Follow with a lemon or orange peel for the smell. Neither is folklore — the ice does mechanical work and the citrus oil cuts the film.
Clean the splash guard, which is where the smell usually is.The rubber baffle at the top of the chamber traps food on its underside and it is almost always the source of a persistent smell. With the unit isolated and unplugged, fold each flap up and scrub the underside with an old toothbrush and washing-up liquid.
Use bicarbonate and vinegar for smells, never bleach or drain unblocker.A few spoonfuls of bicarbonate of soda followed by white vinegar, left to fizz for a few minutes and flushed with cold water, is safe and effective. Chemical drain unblockers attack the metal and seals of a disposal unit and can be thrown back out when it runs.
Check underneath occasionally for leaks.A torch inside the cupboard, looking at the sink flange, the waste connection and the body of the unit. A joint leak is fixable; water weeping from the body itself means the unit is corroded through and needs replacing.
Know where the hex key and the reset button are before you need them.The key is often clipped to the unit or was in the box. Tape it inside the cupboard door. The red reset button is on the underside. Finding both calmly now is much easier than finding them with a sink full of water.

Tips

Cold water for thirty seconds after the noise stops is the single most valuable habit, because most disposal problems are actually waste pipe problems.
A sink strainer over the opening when the unit is not in use stops the teaspoons, bottle caps and packaging tabs that cause most jams.
If the smell keeps coming back after cleaning the chamber, it is the underside of the splash guard. It almost always is.
Grinding a handful of ice with a spoonful of coarse salt scours the chamber a little more aggressively than ice alone, and it is harmless.

Common mistakes

Using it as a bin — It is designed for the scraps left after normal washing up, ground gradually with water running — not for emptying a plate or a peeling bowl into. Loading it is how jams and blockages happen.
Running hot water while grinding — Hot water melts fats which then re-solidify further along the waste pipe, out of reach. Cold keeps them solid so they are ground and flushed through.
Pouring drain unblocker in when the sink is slow — It corrodes the metal components and seals, and the unit can splash it back out. Clear the trap and pipe mechanically instead.
Not using it for weeks at a time — The ring corrodes and the chamber goes stale. Regular short runs with cold water are part of looking after it, not just of using it.

Keeping on top of it

Run cold water for 30 seconds after every use (every use)
Run it briefly even with nothing much to grind (a few times a week)
Grind ice cubes and a citrus peel (monthly)
Scrub the underside of the splash guard, unit isolated and unplugged (monthly)
Check underneath for leaks at the flange, waste connection and body (every few months)

Questions people ask

What should not go in a waste disposal unit?

Fibrous vegetables such as celery, corn husks and onion skins; starchy items such as potato peel in quantity, rice and pasta; fat, oil, coffee grounds and eggshells; and anything hard or non-food — bones, stones, shells, glass, metal, cutlery and plastic. The first two groups block the pipe; the third causes sludge; the fourth jams the flywheel.

How do I stop my waste disposal smelling?

Clean the underside of the rubber splash guard, which is almost always the source. Then grind ice cubes with cold water and follow with a citrus peel. Bicarbonate of soda followed by white vinegar handles the rest. Never use bleach or drain unblocker in a disposal unit.

How long does a waste disposal unit last?

Typically eight to fifteen years in domestic use, and the difference between the two ends of that range is almost entirely what has been put down it. Fibrous and hard items, and running it hot, shorten it noticeably.

Do I need to grind ice cubes to sharpen the blades?

There are no blades — waste is thrown against a fixed grind ring by swivelling lugs, and nothing on the unit is sharpened. Ice does help, but as a scouring agent that knocks residue off the ring and the lugs, not as a sharpener.