How can I tell if I have a septic tank or sewage treatment plant?

A septic tank mainly settles sewage and normally sends liquid to a drainage field. A small sewage treatment plant provides further treatment using mechanical parts, often with a control panel, blower, motor or alarm. Paperwork, a model plate or a competent professional provides stronger confirmation than appearance alone.

Can this tool confirm my drainage system type?

No. It gives a likely indication from the answers selected. It cannot inspect the system, verify a discharge route or replace identification by a competent drainage professional.

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What drainage system do I have?

Q: How can I tell if I have a cesspool?

A cesspool is a sealed holding tank with no discharge. It stores sewage until a registered waste carrier empties it, often much more frequently than a septic tank or treatment plant is desludged.

Answer six simple questions about the system, emptying and discharge. We will show which type the clues most strongly suggest and what to check next.

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This tool provides a likely indication only. It cannot inspect or confirm a system, discharge route or regulatory position.

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Choose the closest answer

0 of 6 answered

“Not sure” is a useful answer. Never open or enter a tank to investigate it.

1. Where does the property’s toilet waste go?

2. Do any records, invoices or labels name the system?

3. What happens to liquid leaving the system?

4. Does it have powered treatment equipment?

5. How often is a tanker normally needed?

6. Is it serviced as mechanical equipment?

Your selections stay in this browser. This free tool does not submit or save them.

The three main private systems

Septic tankSettles sewage and normally sends liquid to a drainage field in the ground.

Treatment plantUses mechanical parts to treat sewage to a higher standard before discharge.

CesspoolA sealed holding tank with no discharge; sewage is removed by a registered waste carrier.

Common questions

How can I tell if I have a septic tank or treatment plant?

A visible model plate, manual, installation record or service invoice is stronger evidence than appearance. Treatment plants normally have mechanical equipment, while septic tanks mainly settle sewage and discharge through a drainage field.

How can I tell if I have a cesspool?

A cesspool is sealed and does not discharge. It generally needs frequent emptying because it stores all sewage rather than releasing treated liquid.

What if the answers conflict?

Do not guess for a house sale. Ask a competent drainage professional to identify the system and trace the discharge arrangement.

Official information: GOV.UK septic tanks and treatment plants and GOV.UK cesspool guidance.