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Building over sewers – avoiding risk for homebuyers and conveyancers

18th February 2020
Industry briefing

The water companies of England and Wales are responsible for a vast network of sewer pipes, just under 450,000km of them in total. These pipes run under the ground all over the country, both in public and private land, connecting the majority of properties to the public sewerage system.


Water companies have statutory rights of access to public sewers and have the right to refuse any development that restricts this, or that could potentially damage their assets. As problems with sewers can cause serious damage to the surrounding area, it’s beneficial to all parties to ensure steps are taken to safeguard both the property and the surrounding sewers.

Nothing can be built over or close to public sewers unless the water company’s consent is first obtained, often in the form of a build over agreement. Anyone planning to build within three metres of a public sewer is therefore required to obtain permission from the relevant water company. There are also rules applying to other assets, such as lateral drains, which tend to vary by company, so it’s always important to check with them prior to any development work.

While water companies will always work with property owners to try and find a mutually agreeable arrangement, there are some circumstances in which permission must be refused due to the nature of the assets. Consent would not be granted to build over a pressurised rising main – where sewage is pumped uphill – or a large strategic sewer, due to the consequences of any potential damage. Restricting a water company’s access to manholes is also not allowed as it limits their access to sewers.

Obtaining a water company’s consent for any building work planned over or near a public sewer is vital. Without consent, your local council’s building control department might not sign off your building regulations completion certificate and without this, you may have problems when trying to sell your property. Water companies have legal powers, under Sections 159 to 171 of the Water Industry Act 1991, giving the right to maintain, repair, replace and renew public sewers. If any building work limits this, the water company could seek an injunction to remove the building and potentially recover damages.

How DWSN members can help

These restrictions highlight the need for a CON29DW Enquiry to be completed for any property transaction, as the report would confirm whether any build over consents are in place. Question 2.7 of the CON29DW asks “has a sewerage undertaker approved or been consulted about any plans to erect a building or extension on the property over or in the vicinity of a public sewer, disposal main or drain?”. This will highlight whether any development was undertaken with the water company’s consent. If there is the possibility of any development at the property affecting a public sewer and that the water company may not have been consulted, or the development approved, it is imperative that the water company is contacted as soon as possible to verify the situation.

With the vast network of public sewers throughout England and Wales, it is not uncommon for both new and existing properties to be built over or near a water company’s asset. While this is always something owners and developers need to be aware of, providing the company is consulted and proper steps followed, it need not be something that deters potential purchasers.

If you want to find out more, use this postcode look-up to contact the CON29DW provider for the address you need to check.