Selling a House with a Septic Tank : Does it comply with legislation?

Homeowners with septic tanks in England need to check if their tanks comply with recent changes in the law governing off-mains drainage. If they don’t, the owners may find it impossible to sell their properties in future.

Thousands of properties in rural areas currently rely on private drainage arrangements, primarily septic tanks, to dispose of wastewater from WCs, bathrooms, kitchen sinks etc.

From January 1 2020, it became illegal for any septic tank in England to discharge effluent directly into a watercourse such as a river, stream or pond; any that do must either be replaced or upgraded.

The change is being applied under the General Binding Rules, which are set by the Environment Agency (EA). The Rules regulate the private drainage systems used by properties which cannot connect to a mains sewer for reasons of distance or topography. They stipulate that homeowners are responsible for ensuring their wastewater treatment systems always operate correctly and don’t cause pollution or other harm to the surrounding environment. In the event of a local pollution incident caused by a poor installation, both the homeowner and their installer are at risk of prosecution by the EA. This carries with it the prospect of a heavy fine and a large clean-up bill.

As the recent change illustrates, the Rules are subject to review and it is incumbent on property owners to stay abreast of any changes.

If a septic tank is discharging directly into surface water, then the choices are either to replace the tank with a sewage treatment plant that carries full BS EN 12566-3 Certification, or to divert the discharge into a drainage field, designed and constructed to BS EN 6297 2007 (assuming a mains sewer connection is impossible).

The law does offer a concession for septics and their drainage fields where these met the relevant British Standard in place at the time of installation. In these instances, the owners may be able to upgrade their system by adding a reed bed or a converter, although this depends on the ground conditions.

The changes were not widely publicised and it appears that, one year on, many owners are still not clear on the full ramifications. The confusion has led to large numbers of rural property owners going online to check whether they are affected.

Why Septic Tanks aren’t a Panacea

To understand the reasons for the change in the regulations it’s useful to have some understanding of how off-mains drainage systems work.

The initial aim should always be to try and connect a property to a mains sewer – if necessary using a pump station – as stipulated in UK Building Regulations. If a connection isn’t possible, then the options for property owners are based around the aforesaid private (aka off-mains) drainage systems.

It’s a fairly safe bet that early consideration will be given to installing a septic tank; anecdotally, they are the most common off-mains product typed into Google. Given the right ground conditions and the addition of a reed bed, they may well be all that’s needed.

But, despite their ubiquity, septic tanks are not always a legally compliant solution for the property or its local environment. Septics don’t actively treat the sewage in the wastewater; instead they create a soluble waste from solids, and rely on the surrounding substrate to complete the job of filtering effluent before it reaches groundwater. This process is compromised if the septic tank is of poor quality or installed in the wrong location (for example on clay soil or where the water table is less than one metre from the surface). If the filtration fails, it can cause localized pollution, a very unpleasant smell, and obviously become a health hazard.

Worryingly, reports from accredited installers show that the number of pollution incidents are rising, and the vast majority of these are either because of inappropriate installations of septic tanks, or poor maintenance.

Sewage treatment plants, by contrast, breakdown the sewage and treat more than 95 per cent of the pollutants before the effluent is discharged into a drainage field. Packaged sewage treatment systems with tertiary treatment such as packaged reed beds are the current ‘gold standard’, bringing the efficiency rating up to 98 per cent. They produce a clear, odourless overflow that is environmentally friendly and suitable for discharging even on sensitive sites, but this is regulated and requires registration with the Environment Agency.

Advice for Septic Tank Owners

No off-mains drainage system is a “fit and forget” solution, but this is particularly true of septic tanks. There are no sensible short-cuts with local wastewater drainage, nor should owners rely on the opinion of unqualified individuals.

For expert guidance on whether a septic tank needs upgrading or replacing, conveyancers can call the Septic Tank Hotline (tel. 01296 633033), or visit here.

More information:

-BS6297 2007: Code of Practice for the Design and Installation of Drainage Fields for use in Wastewater Treatment
-Building Regulations Section H2
Small sewage discharges in England: general binding rules
General binding rules: small sewage discharge to a surface water

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