10 things you should never flush into a septic tank - Proseptic

Unblocktober: Ten things you should never flush into a septic tank

never flush into your septic tank

It’s Unblocktober – the national campaign and awareness month to improve the health of our sewers, watercourses and seas.

To mark the occasion and help British people treat their drains better, we’ve listed ten things you should never flush into a septic tank or sewage treatment plant.

10 things you should never flush into a septic tank


Paints, solvents – even some drain cleaners – many of the chemicals that can pass through your septic tank can cause damage.

Some may disturb the treatment process that takes place within your tank or even corrosion of some parts.

Aside from the environmental cost, careless chemical disposal could result in a financial impact you don’t want.

Sanitary products

Not just feminine products – makeup removal or baby wipes and any other disposable hygiene items can be problematic.

If these aren’t biodegradable, they can cause issues including pump burnout – assuming they even reach the tank without clogging the pipes.

Even if a product is labelled as biodegradable, they still pose a risk that’s better avoided.

Food waste

Food scraps need to go in the bin – they don’t decompose quickly or easily and can contribute to the dreaded phenomenon of ‘fatbergs’.


The main body of a fatberg is, unsurprisingly, fat – grease, oils and other cooking grime poured down the drain.

This can later solidify or build up in bends to block pipes and cause issues with your soakaway system by blocking the perforated holes.

Cigarette butts

They may seem small enough not to cause problems but cigarette butts contain filters that can damage a septic tank pump.

For other items that look little but can cause big problems, see also hair clumps, pet fur and coffee grounds.

Cotton bud and dental floss

Similar to other hygiene products highlighted, these items can cause clogging issues.

But cotton buds and dental floss also offer the added threat of potentially making mechanical elements fail too.


It sounds unlikely but even excess water can overload your septic tank and disturb its internal functions.

But this is easily avoided by ensuring no rainwater downpipes or gullies are connected to your system.

Nappies or cat litter

Both of these contain materials specifically designed to absorb liquid and clump together – fireplace ashes can cause the same issue.

This increases the volume of ‘hard to break down’ solid waste that can block your reservoir.

Paper towels and napkins

They may seem the same as toilet paper but in fact take much longer to dissolve in water and are far more likely to cause a blockage.

Antibacterial products

Just like your guts, there are good bacteria in your septic tank, playing an important role in helping break down solids and sludge.

Antibacterial products can kill them off and stop your system working as well as it should.

Need to know more?

By making sure none of the above make their way into our watercourses, you’ll be contributing to cleaner seas. And you’ll also be giving your septic tank the best chance of staying healthy and functioning properly.

If you need to speak to a professional about repairing or replacing your system, please get in touch today.

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