Buying a house with a septic tank is perfectly normal in rural areas, but it means taking on responsibility for your own sewage treatment, and the rules that come with it. Before you exchange contracts you should know what kind of system the property has, where it discharges, whether it meets the Environment Agency’s general binding rules, and what condition it’s in. A home survey will note the parts that can be seen, but a proper septic tank survey by a drainage specialist is the only way to know how the system is actually working.
Septic tank, treatment plant or cesspit: what’s the difference?
Off-mains properties use one of three main systems, and the agent’s details don’t always get the name right.
| System | What it does | What leaves it |
|---|---|---|
| Septic tank | Settles solids out of the sewage in a tank, where they partly break down | Partly treated liquid, which should go to a drainage field in the ground |
| Small sewage treatment plant (package plant) | Treats the sewage mechanically or biologically, usually with an electric pump or blower | Treated effluent, which can go to a drainage field or, in some cases, a watercourse |
| Cesspit or cesspool | A sealed tank that simply stores sewage, with no treatment | Nothing. It must be emptied by tanker and must not leak or overflow |
The differences matter. A septic tank needs a working drainage field (a network of perforated pipes in gravel trenches that lets the liquid soak away and be cleaned by the soil). A treatment plant needs electricity and servicing. A cesspit needs emptying often, which is an ongoing cost.
The general binding rules for septic tanks
In England, small sewage discharges from septic tanks and treatment plants are regulated by the Environment Agency through a set of general binding rules. If a system meets all the rules that apply to it, no permit is needed. If it doesn’t, the owner either needs a permit or has to bring the system up to standard.
Key points for buyers include:
- Volume limits. The rules cover discharges of up to 2 cubic metres (2,000 litres) a day to the ground, or up to 5 cubic metres (5,000 litres) a day to surface water. A single house will normally be well within these.
- Domestic sewage only, and the discharge must not cause pollution.
- The equipment must meet the relevant British Standard that applied when it was installed.
- Discharges to ground must go through a drainage field, not a well, borehole or old rainwater soakaway. They must not be within a groundwater source protection zone 1, or within 50 metres of a well, spring or borehole used for drinking water or food production.
- Regular emptying (desludging) by a registered waste carrier, and maintenance in line with the manufacturer’s instructions.
The 1 January 2020 deadline: septic tanks discharging to a watercourse
This is the rule that catches buyers out. A septic tank must not discharge directly to surface water, meaning a stream, river, ditch or land drain that runs into one. Under the general binding rules, septic tanks that did this had to be replaced or upgraded by 1 January 2020.
The usual options are to:
- connect to the mains sewer, if one is reasonably close;
- install a drainage field so the septic tank discharges to the ground instead;
- replace the septic tank with a small sewage treatment plant, which can discharge to a watercourse under the rules.
If you’re buying a property with a septic tank that discharges to a watercourse, the government’s guidance is that buyer and seller should agree who will replace or upgrade the system as a condition of the sale. That can be a significant cost, so it belongs in your negotiation, not after completion. Older rural systems in particular were often piped to the nearest beck or field drain, and nobody may have checked since.
Who is responsible for a septic tank?
The government calls the person responsible the operator. For most single houses that’s the owner. A tenant can be the operator if the tenancy agreement makes them responsible for the system.
Shared systems need more care. Across the Pennines and the Yorkshire Dales it’s common for a cluster of converted barns and farm cottages to share one tank. In that case each owner whose property uses the system is an operator, and they are jointly responsible for complying with the rules, and you’ll want to know who pays for emptying and repairs, what happens if it fails, and whether the arrangements are written into the deeds. If the tank or drainage field sits on someone else’s land, your conveyancer needs to confirm you have legal rights to use it, reach it and maintain it.
When a property is sold, the seller must tell the buyer in writing that there’s a small sewage discharge and give a description of the system. This should include the location of the tank, drainage system and discharge point, any changes made, maintenance details and records where they exist.
What to ask the seller
Get these answers in writing, ideally through your conveyancer:
- What type of system is it? Septic tank, treatment plant or cesspit? Manufacturer and model, if known.
- Where does it discharge? To a drainage field or to a watercourse, ditch or land drain? Can they show you the outlet?
- Where are the tank and drainage field? Is any of it on a neighbour’s land, under a driveway, or under an extension?
- How old is it, and has it ever been replaced or altered? Was building regulations approval obtained for a newer installation?
- When was it last emptied, and by whom? Ask for receipts from a registered waste carrier.
- Is there a maintenance manual and service history? This matters especially for treatment plants.
- Does it serve any other properties? If so, what is the written agreement?
- Has there ever been a problem? Ask about smells, slow-draining toilets, sewage surfacing in the garden, or complaints from neighbours or the Environment Agency.
- Is there an Environment Agency permit? If so, it will need transferring.
Vague answers (“it’s never given us any trouble”) are common, especially with older systems. That’s a reason to investigate, not a reason to relax.
What a home survey can and can’t tell you
A home survey looks at the visible and accessible parts of the drainage. In a Home Survey Level 3, RICS guidance says the surveyor lifts accessible inspection chamber covers to drains and septic tanks, where it’s safe to do so and without causing damage, and observes the drains in normal use. That can reveal obvious problems: a damaged cover, a blocked or backed-up chamber, signs of overflow, sewage on the ground, or a tank sitting close to the house or a watercourse.
What a home survey can’t do is test the system. We are building surveyors, not drainage engineers. We won’t put a camera down the pipes, pump the tank out to inspect its walls, test how well the drainage field soaks away, or confirm whether the system complies with the general binding rules. Those need a drainage specialist. See what a Level 2 survey can’t see for the wider limits of a non-invasive survey.
Why a specialist septic tank survey is worth it
A septic tank survey or drainage inspection by a specialist will usually:
- identify the system and confirm where it discharges;
- empty the tank and inspect it for cracks, missing baffles or a broken outlet;
- run a CCTV survey of the pipes;
- assess the drainage field for saturation, ponding or failure;
- advise whether the system meets the general binding rules and what any upgrade might involve.
A failed drainage field or a non-compliant discharge to a watercourse can mean replacing the whole system. The specialist’s report gives you something concrete to negotiate on (see using your survey to negotiate), or a reason to walk away.
Septic tanks in Yorkshire and the Pennines
Plenty of homes in our area aren’t on mains drainage: hill farms and laithe-house conversions above the Calder and Colne valleys, hamlets in the Dales and the Peak fringe, and isolated cottages on the moor edge. A few local factors are worth knowing about:
- Heavy clay and shallow rock. Drainage fields need soil that drains. On waterlogged upland clays or where gritstone is close to the surface, an old soakaway may never have worked well, and a replacement may need a different design.
- Private water supplies. Many rural Pennine properties drink from springs or boreholes, their own or a neighbour’s. The 50-metre rule around drinking water sources matters here, so ask whether there are any private supplies nearby.
- Becks and field drains everywhere. Upland sites often have a watercourse close by, which makes the old “pipe it to the beck” arrangement more likely.
If the house is also old or converted, a Home Survey Level 3 is usually the right starting point. Our guides to which survey level you need and the questions to ask before you offer cover the rest of the checklist.
Next steps
Ask the seller the questions above early, book a specialist drainage inspection alongside your survey, and make sure your conveyancer has the system details and any shared-use agreements. We can carry out the Level 3 survey and tell you what we can see of the drainage, alongside everything else about the building. Get in touch with the address for a fixed quote.
Sources and further reading
- Septic tanks and sewage treatment plants: what you need to do — GOV.UK
- General binding rules: small sewage discharge to a surface water — GOV.UK (Environment Agency)
- General binding rules: small sewage discharge to the ground — GOV.UK (Environment Agency)
- Septic tanks and sewage treatment plants: your property has a cesspool — GOV.UK
- Scope of inspection: Home Survey Level Three — RICS