Home / What Not to Put Down a Waste Disposal

Waste disposal units offer a convenient means of getting rid of food waste, but they can’t chew up anything – there are limits to what they can do.

Here are ten things you should never put down your waste disposal unit.


Grease, oil, butter and so on are nice and runny when they’re hot, so you might think nothing of pouring them down the sink.  Unfortunately when they cool they solidify, and cause blockages (including some truly enormous ones). You should never pour fats down the sink anyway, and having a waste disposal unit doesn’t change this.


Pasta, rice, beans and potato peelings tend to expand as they absorb water – and since your waste disposal is built to shred them to tiny pieces, the resulting pulpy soup is very likely to cause a blockage.  Stick this sort of thing on the compost heap instead.


Even the strongest waste disposal units will struggle to grind up bone.  Those that do find their way into the pipes tend to do so in oversized chunks, which can cause problems.


Flour is used in cooking to absorb liquid and make a paste.  Of course, that paste and your plumbing don’t mix – so don’t put flour down the waste disposal.

Ground Coffee

Ground coffee readily absorbs water, so when it finds its way into the plumbing it’ll turn into a foul-smelling sludge that’ll take weeks to decay.  Don’t put coffee down your waste disposal unit – put it on the compost heap.


You might not think of celery as something that could cause problems, but unfortunately it’s made of long, stringy fibres which can wrap around the inside of a waste disposal unit.  The same is true of asparagus.


While small seeds are fine, the stones you get in a plum or avocado are generally too large and tough to be properly ground up.  As such, they’ll stick around in your waste disposal.  The same is true of coconut shells and other items of a similar firmness.


While the shells themselves aren’t too much of a problem, the membrane that lines the interior can be, since it can wrap around the inside of the unit and wreak havoc.

Onion skins

This one’s a little bit more contentious, as you might be able to get away with the occasional onion -but onions also come with a membrane that can sometimes stick to the inside of the unit.  Add them to the compost heap instead.

Non-food items

This general term encompasses anything that isn’t food – everything from a runaway fork that you might have accidentally dropped in there, to cigarette butts or food packaging.  Don’t be lazy – stick them in the bin, instead.

Call Us