Looking after your septic tank: maintenance dos & don'ts

Looking after a septic tank comes down to a short list: empty it regularly, only flush the 3 Ps (pee, poo and paper), keep fats, wipes and chemicals out, and protect the drainage field from damage. Get those right and a septic tank needs very little else.

Do

• Empty it on schedule. Most family tanks need it roughly every 1–2 years, depending on tank size and occupancy — see how often to empty. This is the single most effective thing you can do to prevent every other problem on this list.
• Only flush the 3 Ps — pee, poo and toilet paper. Everything else should go in the bin.
• Spread out heavy water use — a full load of laundry back-to-back with a dishwasher and several showers can overload a tank’s normal cycle; spacing it out gives the system time to settle.
• Watch for early warning signs — see signs your septic tank needs emptying and common septic tank problems.
• Keep records — a waste transfer note from every emptying, and servicing records for a treatment plant, are both required under the General Binding Rules and useful if you ever sell.

Don’t

• Don’t flush wipes — including ones labelled “flushable.” They don’t break down like paper and are one of the most common causes of blockages.
• Don’t pour fats, oils or grease down the sink. They solidify and clog pipework and the tank itself.
• Don’t flush nappies, sanitary products, cotton buds, cigarette ends or medicines.
• Don’t pour large quantities of harsh chemicals or bleach down the drain. A septic tank relies on bacteria to work — heavy chemical use can kill them off.
• Don’t drive, park, or build over the drainage field, and don’t plant trees or shrubs with invasive roots near it — both can damage the pipework.
• Don’t rely on additives instead of emptying (see below).

The additives myth

Septic tank “treatments” or additives are widely sold, but generally aren’t needed. A septic tank already relies on naturally occurring bacteria present in ordinary household wastewater to do its job — you don’t need to add more. Some additives can even be counterproductive, disrupting the tank’s balance or, in some cases, damaging pipework. Regular emptying and sensible use are what actually keep a system working, not additives.

Treatment plants need a bit more

If you have a sewage treatment plant rather than a septic tank, the same dos and don’ts apply, plus annual servicing to the manufacturer’s schedule. A treatment plant that isn’t serviced can drift out of compliance even if it looks fine day to day — see our sewage treatment plants guide.

Ready to book?

See emptying & servicing to get your system on a proper schedule, or run the emptying diagnostic to check whether you’re due now.

Sources: GOV.UK — General binding rules: small sewage discharge to the ground