Buying a property that is not on mains drainage: what housebuyers need to know

If you are buying a house in a village, on the edge of a town or out in the countryside, one of the practical issues to check at an early stage is how the property deals with foul drainage. About four percent of the UK population is currently believed not to be connected to the mains sewer and to rely either on a septic tank, a package treatment plant or, less commonly, a cesspit. That does not make the property a bad buy, but it does mean there are some extra practical and legal questions to answer before you commit yourself.

How common are septic tanks in East Anglia?

There is no single up-to-date official figure published specifically for East Anglia identifying exactly how many properties still use septic tanks but with its large number of villages, farmhouses, converted barns and edge-of-settlement homes, the proportion is likely to be higher in some localities than the national average, particularly in more rural parts of Norfolk, Suffolk and Cambridgeshire.

In other words, a septic tank is not an unusual feature of properties in this part of the country. It is, however, something your conveyancing solicitor should investigate carefully, because the condition, location and legal compliance of the system can affect both value and future expense.

What will it cost to empty a septic tank?

Costs vary depending on the size of the tank, how easy it is to access, where the property is located and how frequently the system is emptied. Current UK pricing guides suggest that a standard domestic emptying visit is often in the region of £170 to £300, with many typical households paying around £200 to £225 for a routine empty. If your system is straightforward and emptied regularly, that may be the whole story. If access is awkward, the tank is larger than average or additional cleaning is needed, the figure can rise.

For an average household, a sensible working budget is often around £200 to £300 a year if the tank needs emptying annually. Some households empty less often, while others with heavier use may need more regular servicing. Buyers should therefore ask not only what the last emptying cost was, but also how often the seller has actually needed to arrange it.

What are the legal restrictions on septic tanks?

In England, septic tanks and small sewage treatment systems are regulated primarily through the Environment Agency’s General Binding Rules. These rules are important because they determine whether the system can be used without an environmental permit. A buyer should not assume that an older system is exempt simply because it has been there for many years.

The most widely known rule is that a septic tank must not discharge directly into surface water, such as a ditch, stream, river, canal or lake, unless there is a permit in place, in very limited circumstances. In most ordinary residential situations, a septic tank should discharge to the ground through a drainage field. If the existing set-up sends effluent straight into a watercourse, that is likely to require upgrading or replacement. There are also rules about proper installation standards, maintenance, emptying by an authorised person, and the volume and location of the discharge.

The rules do not apply only to brand new tanks. The current guidance distinguishes between an existing discharge and a new discharge. Broadly speaking, an existing discharge is one from a system installed before 2 October 2023 which has not been changed significantly since then. A new discharge is one from a system installed, or significantly changed, on or after that date. Existing discharges may be treated differently in some respects, but they still have to comply with the relevant rules. That means an older system can still be non-compliant, and if it is, the problem usually passes to the buyer on completion unless it is dealt with during the transaction.

This matters because the cost of putting an unlawful or failing system right can be significant. Depending on what is wrong, the solution may involve new drainage field works, replacement with a treatment plant, rights over adjoining land, building regulations, planning issues and practical disruption after you move in.

What should your conveyancing solicitor ask before you buy?

A careful conveyancing solicitor will want more than a simple confirmation that the property has a septic tank. The important point is whether the system is lawful, serviceable and adequately documented. Questions commonly include the following.

• What type of system serves the property: septic tank, sewage treatment plant or cesspit?
• Where exactly is the tank, drainage field and all associated pipework located?
• Is the system within the property boundaries, and if not, what legal rights exist for use, access, repair and replacement?
• Where does the discharge go: to a drainage field in the ground or to a watercourse?
• Was the system installed as an existing discharge or a new discharge, and has it been altered significantly in recent years?
• Does the seller believe the system complies with the General Binding Rules, and if so, on what basis?
• Is there an environmental permit, and if there is, can it be transferred on completion?
• When was the tank last emptied, how often has it been emptied and by whom?
• Are there maintenance records, invoices, plans, specifications, warranties or service reports?
• Have there been any blockages, smells, overflows, flooding issues, repair works or complaints from neighbours or regulators?
• Who is responsible for maintenance and cost if the system is shared with other properties?
• Are there any building regulation approvals, planning permissions or completion certificates relating to the installation or later works?

Depending on the replies, your solicitor may also advise you to obtain a specialist drainage inspection in addition to your usual survey. That can be particularly sensible where records are missing, the system is old, the discharge arrangements are unclear, or there is any suggestion that the tank may drain directly to a ditch or stream.

Final thoughts

Buying a property without mains drainage need not be a deal-breaker. Many desirable homes across East Anglia rely on private systems. The key is to make sure you know what you are buying. Clear answers about compliance, maintenance history, running costs and legal rights can help you avoid an unpleasant surprise after completion and, where necessary, strengthen your hand in renegotiating price or requiring remedial works before you exchange contracts.

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In order to protect client anonymity, the initials in the above case study have been changed and do not relate the the client or other parties in any way. This article aims to supply general information, but it is not intended to constitute advice. Every effort is made to ensure that the law referred to is correct at the date of publication and to avoid any statement which may mislead. However, no duty of care is assumed to any person and no liability is accepted for any omission or inaccuracy. Always seek advice specific to your own circumstances. Fraser Dawbarns LLP is always happy to provide such advice.