Septic Tanks and Treatment Plants: Avoid Falling Foul of the Rules

Over the past six or so years, a number of updates to the law governing the discharge of sewage have bred confusion amongst homeowners, homebuyers and, indeed, solicitors. This article aims to briefly summarise the position and to help those affected to avoid falling foul of the rules.

When do the rules apply?

Most properties are connected to a mains sewer and, therefore, are not the subject of this article. Properties not connected are likely to be served by either a cesspool, septic tank or sewage disposal system, in which case the legislation is applicable.

A minority of properties may be served by a less traditional system, with Government guidance listing a ‘reed bed’ or ‘trench arch system’ as possible, alternative examples. Non-standard disposal methods such as these are not discussed further here but if your property is not connected to a mains sewer, nor using a septic tank, cesspool or sewage disposal system, you should contact the Environment Agency for specific guidance. 

Cesspool, Septic Tank or Sewage Disposal System?

Cesspools/cesspits are, essentially, basic holding chambers for waste. The rules in this regard are relatively straightforward – any cesspool must be maintained and regularly emptied (typically, at least once per month) to prevent any leaks or overflow. If installing a new cesspool, you must obtain planning permission and building regulations approval, and ensure sufficient capacity (a minimum of 18,000 litres per 2 users, plus another 6,800 litres for each extra user).

If your property is served by a septic tank (an underground tank which collects solid waste and redistributes liquid waste to the ground) or a sewage treatment plant/package treatment plant (a more advanced, mechanical system which treats the waste), the starting point is to determine whether an Environment Agency permit is required.  

“Operators” of septic tanks and treatment plants must obtain a permit from the Environment Agency unless the system in question complies with the “general binding rules”.

An operator is the person responsible for the system. This will typically be the owner of the property on which the system is located but there may be several operators (where one system serves several properties), or a tenant may be deemed to be the operator where the relevant lease/agreement places maintenance responsibility onto that tenant.

General binding rules

An Environment Agency permit will not be required if the sewage is domestic in nature, does not cause pollution and does not drain to ground or surface water.

“Domestic” does not mean residential only, while Government guidance regarding pollution suggests a common sense approach should be applied – are sewage smells particularly noticeable, or are there indicators that sewage is not draining properly (i.e. are there pools of water in the area that the sewage is released)?

Ground Water Discharge

If releasing sewage to the ground, the tank/plant must meet the necessary British Standard, be regularly emptied and maintained, and be of appropriate size for the property. You must also install a drainage field to act as an infiltration system. Even if complying with these points, a permit will still be required if:

  • the sewage is discharged to a well, borehole or other deep structure;
  • the daily discharge exceeds 2,000 litres per day; or
  • the discharge point is in or near to a groundwater source protection zone (generally, an area containing a private or commercial water supply).

Surface Water Discharge

The water discharged must be sufficiently clean, meaning that a standard septic tank will not be suitable – a sewage treatment plant will be required. In addition, the daily discharge must not exceed 5,000 litres per day.    

When was the system installed?

To further complicate matters, the rules and regulations differ depending on whether the discharge commenced on or after 1 January 2015. If so, or if the nature of an existing discharge was altered after that date (for example, a discharge to surface water becomes instead a ground water discharge, or a new drainage field has been installed), you must also bear in mind the following:

  • new installations are subject to building regulations approval (and possibly planning permission);
  • a new installation generally will not be permitted (without good reason) if the property falls within 30 metres of a public sewer;
  • discharges within designated, sensitive areas (ancient woodland or within 50 metres of any special area of conservation, special protection area, Ramsar site, or site of special scientific interest) will require an Environment Agency permit.

Further Guidance

While the above is not intended to be an exhaustive discussion of the legal requirements, we hope that this article provides clarity on some of the more immediate concerns relating to private sewage disposal.

This has clearly become a complex area of law and is subject to further change (particularly in light of Brexit); should you have any doubts as to whether a permit is required for your installation, or whether a new installation will be permitted, you should contact the Environment Agency and/or obtain advice from a suitably qualified drainage engineer.    

Our content explained

Every piece of content we create is correct on the date it’s published but please don’t rely on it as legal advice. If you’d like to speak to us about your own legal requirements, please contact one of our expert lawyers.

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