Our drains were never designed to handle the levels of toxic waste we flush down the drain. They were designed in the 1800s before most of the toxic chemicals we use in our homes were even developed (Science Museum).
Since then our use of chemicals has exploded – global chemical production has increased fifty fold since 1950 and is forecast to triple by 2050. 140,000 new chemicals have been synthesised since 1950 (The Lancet Commission) (UK Gov).
Toxic chemicals can damage plumbing, disrupt sewage treatment and pollute our rivers and groundwater. They can create safety risks in domestic homes and septic tanks.
What not to flush away:
- Paint, thinners and solvents
- Disinfectants, bleach and acids
- Antibacterial cleaners and pesticides
- Medicines and pharmaceuticals
- Flammable substances
- Oily food residue
- Hygiene products
Toxic chemicals and cleaning products like paint, disinfectant and antibacterial cleaners can poison treatment processes and harm aquatic life (Delphis Eco). Many of the chemicals we flush down the drain end up back in our surface and groundwater. This then runs into the oceans and is consumed by fish, or it is used to water crops, and ultimately it ends up back on our dinner plates.
Drinking water in the UK is collected from rivers and reservoirs, screened, clarified, allowed to sediment, filtered for impurities, pesticides and synthetic chemicals, disinfected with chlorine and UV treatment and pH adjusted (Thames Water). It is ‘among the best in the world’.
Waste water, the water that goes down your drain from the sink, toilet, shower or washing machine, is also supposed to be treated before it is discharged into our rivers and reservoirs (Brita). But Surfers Against Sewage and the recent Channel 4 documentary Dirty Business highlighted the fact that untreated sewage water is frequently released into our rivers and oceans by water companies. 291,492 times in 2025 (The Rivers Trust).
Unused medicines and drugs like painkillers, antibiotics and hormones can also enter our waterways and affect the wildlife in them and the water quality. In Northern Ireland, 91% of the water that was sampled had traces of pharmaceuticals in them (BBC). This has the potential to affect wildlife and more importantly risk that bugs become resistant to drugs, especially antibiotics. Unused medicines should always be returned to the pharmacy for safe disposal.
Flammable substances like fuel, petrol, aerosols and other reactive chemicals carry the risk of fire and explosion if they are flushed down sinks, toilets and outside drains into septic tanks. Some liquids which you may not think are flammable – antifreeze, hobby chemicals like varnishes, motor oils – can contaminate water systems in very small quantities. Think about how oil spills can spread and cause destruction to local wildlife.
Aside from these examples, other items that should never be flushed down the drain include oily food residue like oil, fat and grease, and hygiene products e.g. wet wipes, dental floss, nappies, cat litter, plasters and sanitary products which may not be toxic (though some are) but do cause blockages in the sewer system.
Wherever possible choose eco-friendly and non-toxic products for your home and business. Our business directory is full of companies that make products that are cleaner for the environment and safer to use in your home. These include cleaning products, cosmetics, toiletries, paint manufacturers and more.
And always avoid putting anything down the drain that will be harmful if it ends up in our waterways and rivers.