What happens if you put Bleach, drain cleaner and household chemicals in the wrong bin?

Never mix bleach with acid or ammonia cleaners — that reaction makes chlorine gas in the room you are standing in. Never pour drain cleaner into a bin; it burns through the bag and injures the crew.

Where do Bleach, drain cleaner and household chemicals go?

Use them up as directed if you can. Anything left over goes to hazardous waste, in its own container.

Hazardous waste collection

Diluted household bleach used for its intended purpose ends up in the sewer anyway and is dealt with by treatment; the problem is quantity and mixing. Bleach and any acid — including limescale remover — produce chlorine gas, and bleach with ammonia produces chloramines, both in the confined space of a sink or a bin. Caustic drain cleaner poured into a bin bag burns through the bag and then through whatever it lands on. Use products up, keep them in their own labelled containers, and take the remainder to a household hazardous waste collection. How your area runs hazardous waste collection — a site, an event, or a booking — is worth knowing before you need it.

How to prepare it

Use up as directed rather than disposing, where that is possible.
Keep the original labelled container and the cap.
Take unused concentrate to a hazardous waste collection.

What not to do

Never mix bleach with acid or ammonia cleaners — that reaction makes chlorine gas in the room you are standing in.
Never pour drain cleaner into a bin; it burns through the bag and injures the crew.

Kerbside collection rules genuinely vary by council and county, and local rules always win over general guidance. The reasoning above is what transfers — if your service differs, it will usually be for a reason described here.

Other things that go to hazardous waste collection

Paint thinner, white spirit and turpentine Hazardous waste collection. Flammable, and lethal to a septic tank or a river.
Pesticides, weedkiller and insecticide Hazardous waste collection, in the original container with the label intact.
Asbestos Do not break it, do not drill it, do not sweep it. It needs a licensed route, and most household waste centres take it only by prior arrangement.
Old petrol and diesel Hazardous waste collection. Stale fuel is still fully flammable.
Mercury thermometers and thermostats Hazardous waste. Never in a bin, and never vacuum a spill.
Antifreeze and screenwash Hazardous waste. Ethylene glycol tastes sweet and kills cats, dogs and children.
Fertiliser, lawn feed and pool chemicals Hazardous waste. Oxidisers and concentrated fertiliser are reactive, not just polluting.

Common questions

Where do Bleach, drain cleaner and household chemicals go?: Use them up as directed if you can. Anything left over goes to hazardous waste, in its own container.
What happens if you put Bleach, drain cleaner and household chemicals in the wrong bin?: Never mix bleach with acid or ammonia cleaners — that reaction makes chlorine gas in the room you are standing in. Never pour drain cleaner into a bin; it burns through the bag and injures the crew.

Where do Paint thinner, white spirit and turpentine go? Hazardous waste collection. Flammable, and lethal to a septic tank or a river.
Where do Pesticides, weedkiller and insecticide go? Hazardous waste collection, in the original container with the label intact.
Where do Asbestos go? Do not break it, do not drill it, do not sweep it. It needs a licensed route, and most household waste centres take it only by prior arrangement.
Where do Old petrol and diesel go? Hazardous waste collection. Stale fuel is still fully flammable.
Where do Mercury thermometers and thermostats go? Hazardous waste. Never in a bin, and never vacuum a spill.
Where do Antifreeze and screenwash go? Hazardous waste. Ethylene glycol tastes sweet and kills cats, dogs and children.
Where do Household batteries (AA, AAA, C, D, 9V) go? Shop or manufacturer take-back
Where do Lithium-ion batteries go? Shop or manufacturer take-back
Where do Vapes and disposable e-cigarettes go? Shop or manufacturer take-back
Where do Medicines and tablets go? Pharmacy
Where do Pizza boxes go? Kerbside recycling bin
Where do Leftover wet paint go? Household waste recycling centre

Sources

US Environmental Protection Agency — EPA (Public domain (US Government))

How these figures are compiled and checked