Private drainage systems on third party land – all the information you need at your disposal…

Buying a property with a private drainage system, such as a septic tank, comes with an array of factors to consider. However, those factors are amplified when the system is located on land that is not part of your property.

The first and most pressing concern is to understand how a system on third party land works (for example, who uses it, rights to use it, access for maintenance, splitting maintenance costs).

You also need to consider whether the drainage system complies with the General Binding Rules.

How the drainage system works

Where a drainage system is located on third party land it may either be used exclusively by your property, or sometimes is shared with neighbouring parties.

Where the drainage system is located on neighbouring land you should ask the question:

‘Does the title to the property have a sufficient legal easement for use of, and access to, the drainage system (for repair and maintenance)?’

The length of time the drainage system has been there should also be considered. There may be the possibility of acquiring an easement due to a long historic period of use. If this is the case, and you are buying the property in question, you should obtain a statement of truth or statutory declaration. The statement can be from the seller, or the neighbours on whose land the drainage system is located (if amenable and with sufficient period of knowledge), which will confirm the length of use. This will support an easement application at the Land Registry.

If the drainage system is shared with neighbouring properties you should make enquiries as to how many share the system, any maintenance regimes and costs, and consider a survey to ensure there are no issues.

The General Binding Rules

Drainage systems can either be:

• Cesspits/cesspools - these are sealed tanks that collect effluent, but don't discharge any liquid residue to the surrounding land.
• Septic tanks – these collect effluent and historically then filter liquids out over a 'soakaway' or 'drainage field'. Soakaways are no longer permitted and need to be upgraded to a drainage field. It is also illegal to discharge effluent into a watercourse from a septic tank without an environmental permit. Without such a permit, the septic tank would need to be upgraded to a sewage treatment plant (mentioned below) or connected to the public foul sewer, however this may not be possible.
• Sewage treatment plants - these clean the effluent to a greater degree, and so can sometimes discharge into ditches or watercourses.

The General Binding Rules (the guidance to which was most recently updated in 2023) govern situations where a septic tank or small sewage treatment plant discharges waste water to surface water (such as a stream or other watercourse). They therefore do not apply to cesspools.

Where a drainage system which is subject to the General Binding Rules doesn’t comply with them, the person responsible for it must either connect it to a public foul sewer, or change the system so that it complies. If neither of these things are possible, the operator must apply for a permit. Note that a permit won’t be granted if the Environment Agency think it is reasonable for the operator to connect to the public foul sewer, or that it could meet the General Binding Rules by making changes to the system.

The guidance to the General Binding Rules particularly notes that, in the case of septic tanks, prior to a sale an agreement taking responsibility for the replacement or upgrading of the septic tank should form part of the sale negotiations.

Once you have determined that the General Binding Rules apply, which ones the system needs to comply with depends in part on when it was installed. The key dates are:

• discharges starting before 1 January 2015
• discharges that started after 1 January 2015 but before 2 October 2023; and
• discharges starting after 2 October 2023.

Some of the rules apply to all discharges irrespective of when the system was installed. Examples include:

• limits to discharge volumes
• the type of waste that may be discharged; and
• ensuring that any discharges are not in a groundwater source (protection zone 1) without an environmental permit.

On a sale, it is therefore important to determine the nature of the drainage system in order to assess whether the General Binding Rules apply, how the system complies with them, and if an agreement for upgrading or replacing the system will be needed.

Please note that building regulations and planning permission may also have been, or will be, needed for any drainage system.

Key takeaways:

• If the drainage system is on third party land, it is important to establish that there are adequate rights to use it.
• The application of the General Binding Rules depends on the nature of the drainage system and the date of commencement of discharges.
• It may be necessary to agree to upgrade or replace any non-compliant septic tank as part of a sale.