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CooperBurnett Solicitors | Is your Private Drainage Compliant | Private drainage systems must be compliant by 1 January 2020.

By Glen Webb, Associate Solicitor

At CooperBurnett, we deal with a large number of transactions involving rural properties with private drainage systems. Many property owners are not aware that they must ensure their drainage system complies with regulations introduced in 2015 called General Binding Rules for Small Sewage Discharges (SSDs). Private drainage systems must be compliant by 1 January 2020.

There are three main types of private drainage:

1. Septic tanks;

2. Sewage treatment plants;

3. Cesspits/cesspools.

1 and 2 are affected by the Regulations as they involve discharge of waste water into the environment. Compliance is key to avoiding any potential delays when selling your property.

Septic tanks

A septic tank separates waste water and then discharges it into either a local watercourse (ditch, stream, river etc), or a drainage field (enabling the waste water to trickle through into the ground for further treatment by soil bacteria).

Under the General Binding Rules, septic tanks are no longer permitted to discharge directly into a watercourse. You must replace or upgrade your system before the 2020 deadline or sale of your property, whichever is sooner. 

To replace it you can either install a drainage field so that the waste water disperses into the ground or look to replace your septic tank with a sewage treatment plant. Any replacement or upgrade must comply with the relevant British Standards and be certified as such. You must also seek the relevant planning permission and buildings regulations approval.

If you upgrade your septic tank, you must ensure it is large enough for the purpose, which is based on the maximum daily volume of discharge. 

If the system discharges more than two cubic metres a day into the ground you will need to apply to the Environment Agency for a permit. The installation must be in accordance with the manufacturer’s installation specifications and the drainage field must be designed in accordance with BS6297:2007.

It should be noted that you cannot install a new drainage field if any part of the building the septic tank system serves is within 30 metres of a public sewer. If this is the case, you must connect to the public sewer.

If you sell a property with a septic tank you are obliged to inform the new owner, in writing, that they are responsible for a septic tank discharge and you must include a full description of the system and its location and maintenance obligations.

Sewage treatment plants

A sewage treatment plant is a system which includes a slotted network of pipes which provides secondary treatment for the waste. This means that the waste water is treated so that it is clean enough to discharge into a watercourse as well as a drainage field.

This system must comply with the British Standards and have full BS EN 12566-3 Certification and have a CE mark. Again, any installation must comply with planning permission and buildings regulations approval.


This type of system does not discharge any waste into the surrounding environment and only leaves the tank when it is emptied. There is no treatment involved.


Whether you are buying or selling, if the property has private drainage you must consider if the current system is compliant with the General Binding Rules and, if not, a suitable upgrade or replacement is needed.  A private drainage surveyor would be able to inspect the system and advise; and a buyer of a property with a private drainage system should, if they are in any doubt, undertake a private drainage survey by a qualified drainage expert.

If you wish to discuss any matters arising out of this article, please contact Glen Webb in our Residential Property team on tel: 01892 515022 or by email:


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February 19, 2019
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