How do I find out if my house has a septic tank?

Check your water bill first: if you are only billed for water supply and there is no wastewater or sewerage charge, you are almost certainly on a private system. Other reliable signs are inspection covers in the garden away from the house, a vent pipe near a boundary, an area of grass that is greener or lusher than the rest, and — for buyers — the drainage and water search, which states whether the property is connected to the public foul sewer.

Does no sewerage charge on the water bill definitely mean a septic tank?

It means you are not paying for public sewerage, which almost always means a private system — but not necessarily a septic tank specifically. It could be a sewage treatment plant, a cesspit, or a shared system serving several properties. The distinction matters because the rules and running costs differ, so once you know you're off mains the next step is identifying which system you have.

Where would a septic tank be located?

Usually buried within a few metres of the house on the side the drains leave, marked by one or two inspection covers — often round concrete or green/black plastic lids — with the drainage field beyond it, frequently under lawn. Older tanks can be further away, across a track, or occasionally on a neighbour's land. Following the route from an inside soil pipe to the external inspection chambers usually finds it.

I've discovered my house has a septic tank — what am I responsible for?

As the operator of the system you are responsible for maintaining it, emptying it regularly, and ensuring its discharge meets the General Binding Rules — including the 2020 rule that a septic tank must not discharge directly to a watercourse. Responsibility transferred to you when you took ownership, whether or not anyone mentioned it during the purchase.

Can a house be connected to mains water but not mains sewerage?

Yes, and it's very common in rural Cornwall — mains water reaches far more properties than public sewers do. Being billed for water supply says nothing about your drainage. The wastewater side has to be checked separately, which is exactly what catches out buyers who assumed 'mains water' meant 'mains everything'.

Does my house have a septic tank? How to find out

It sounds like a question nobody should need to ask — but people ask it constantly, usually in one of three situations: they’ve just moved in and something smells; they’re buying and the paperwork says something unexpected; or a water bill, a solicitor or a neighbour has just used the words “private drainage” for the first time.

Here’s how to answer it in ten minutes, in order of reliability.

1. Read your water bill

The single most reliable check. A property on public sewerage pays a wastewater / sewerage charge — in Cornwall, on a South West Water bill. If your bill is water supply only, you are almost certainly on a private system. Mains water and mains sewerage are separate networks, and in rural Cornwall the water main reaches many places the sewer never has.

2. Walk the garden

Physical signs, best read together:

Inspection covers away from the house — one or two lids (round concrete, or green/black plastic) a few metres out, on the side your drains exit. That’s the tank.
A vent pipe — a plastic or cast pipe standing near a boundary or over the tank.
A stretch of noticeably greener grass — the drainage field quietly feeding the lawn.
No public manhole in the lane and no sewer covers between you and the road.

3. Check the paperwork

The drainage and water search from your purchase — the line about connection to the public foul sewer settles it. What that search does and doesn’t reveal is covered in the drainage and water search when the house is off mains.
The seller’s property information form, which asks directly about the sewerage arrangement.
Deeds and old invoices — emptying receipts from a tanker firm are a giveaway, and deeds sometimes record rights over a shared system.

4. Ask the people who’d know

Previous owners, long-standing neighbours (on the same lane, drainage arrangements tend to rhyme), or any local tanker operator who may literally have your address in their round.

5. Identify which system — it changes the rules

Off mains established, the next question is what you actually have, because the obligations differ:

System	Tell-tale	The obligation that matters
Septic tank	two chambers, no machinery, no power feed	must discharge to ground, not to a watercourse
Treatment plant	hum of an air blower, a control box, a power feed	annual servicing with records
Cesspit	no outlet at all — fills up	frequent, expensive emptying
Pumping station	green kiosk or cover with a pump	establish whose it is — some transferred to the water company

How a septic tank works covers the mechanics if the term itself is new to you.

What you’re now responsible for

The uncomfortable part: as the property owner you are the operator of the system, responsible for maintaining it, emptying it on schedule, and meeting the General Binding Rules — and that responsibility landed on you at completion, whether or not anyone pointed it out.

The good news is that finding out is the hard part, and you’ve done it. The free compliance checker turns what you’ve found into a clear position on the 2026 rules in about two minutes — and if the discovery came with a smell or a soggy lawn, start with septic tank smells instead.