Build-over and diversion agreements
From applying for your agreement to the finished build-over or diversion.
Certified contractors
We’re approved contractors for Thames Water, Anglian Water and Southern Water for build-over and diversion work.
50+ years experience
We leverage our years of industry expertise to help you save money and time on your project.
Free advice available
We’re happy to provide you with free advice and a free no-obligation quote - we’re here to help.Full management of your sewer diversion or build-over
If you’re planning to add an extension, conservatory, annexe or garage to your home, then you’ll need to consider the existing drainage pipes that sit under your property. It’s not uncommon for foul and surface water sewers to run through your land – and you need to ensure that your local water authority can access them if they need to service, maintain or repair them.
This means that you might need to apply to build over or divert a sewer. If you’re building within 3 metres of a public sewer or within 1 metre of a public lateral drain, you’ll need approval before work starts.
At Premier Drainage Solutions, we can handle the entire process, from applying for a build-over or diversion agreement to completing the physical work. We’re approved contractors for Thames Water, Anglian Water and Southern Water, operating across the entire south and east of England.
We’ll carry out CCTV drain mapping to understand where the pipes are and whether your building work will affect them. Depending on what we find and what you want to build, you may need to apply for a build-over agreement or a diversion agreement.
Our team will apply for the right agreement for you, and once approved, start the work to divert the sewer if required. We’ll keep you informed every step of the way.
What is a build-over agreement?
A build-over agreement is a contract between you and your sewer provider when you’re building over or very near to a public sewer or lateral drain. The agreement shows that they are happy they have appropriate access to maintain or repair the sewer network if they need to, and that your works won’t affect the structural integrity of the sewer pipe.
You’ll need to apply for a build-over agreement if you’re building something new, such as a house, extension or garage, and there’s a public sewer where you want to put it. You may be able to self-certify the work if you’re adding a structure to an existing building, but every water authority has different requirements.
The Premier Drainage Solutions team will handle the entire build-over process for you, whether you can self-certify or need to apply for a formal build-over agreement.
How does a sewer diversion work?
Under Section 185 of the Water Industry Act 1991, you can request that your local water authority undertake a reasonable diversion of a public sewer. We deal with all the paperwork for you and can carry out the work as an approved contractor. Here’s a brief overview of the process:
- Submit application – This includes the design and specification, and it’s good practice to also include a drawing of the existing sewer with the new development outlined over the top, plus a separate drawing showing the new diversion.
- Technical review and decision – The local water authority conducts a review to determine if the sewer is strategic (crucial) in nature. Within 28 days of receiving all information, they will send their technical decision and next steps.
- Legal agreement – If approved, you’ll sign the legal agreements and tell the water authority when the diversion works are due to take place.
- Construction and inspection – Our team performs the diversion works. We’ll then book a date for a water authority field engineer to inspect the works and advise on any correction actions.
- Sign off and completion – We provide as-built drawings and CCTV surveys to the water authority. They will issue a provisional vesting certificate, followed by a final inspection and completion certificate after a one-year maintenance period.
With our team handling the entire process, almost all communication will occur between us and the water authorities, so you won’t need to worry about phone calls and reviews.
Why choose Premier Drainage Solutions?
By choosing to work with Premier Drainage Solutions, you’ll benefit from a team of fully-certified professionals with over 50 years of industry experience. We are leaders in our field, which we prove time and time again in the way we conduct our work, the specialist equipment we use, and our commitment to outstanding customer service.
We’re approved contractors for Thames Water, Anglian Water, and Southern Water, meaning we can complete build-over agreements and carry out sewer diversion work across the south east of England. Our quality management system meets ISO 9001:2015 standards, and we’re certified to connect to public sewers. We offer end-to-end support, from making your application to making good after diverting a sewer – so we’re there from start to finish.
Build Over and Diversions FAQs
How much does a build-over agreement cost?
How much a build-over agreement costs varies depending on the size of the sewer (based on class) and the water authority’s processes and requirements.
For Southern Water, Anglian Water and Thames Water, costs range between £130 and £1,700, depending on the class of sewer and whether legal work is required.
You’ll also need to pay for the diversion work itself. Contact us for a free quote.
How hard is it to get a build-over agreement?
In general, it’s not that hard to get a build-over agreement as long as you follow the process correctly. If you don’t know what you’re doing or you fail to give the water authority all the information they need, this could delay the process and impact your building timeline.
We’d always recommend using an approved contractor to handle your build-over agreement to ensure everything is dealt with efficiently.
Can a build-over agreement be rejected?
A build-over agreement can be rejected if the water authority thinks that the development risks damaging or limiting access to repair or maintain a sewer. That’s why it’s important to use a sewer and drainage specialist who understands how the process works to ensure your application is approved.
In cases where your build-over agreement is rejected, you should work with your local water authority and your specialist to come up with an alternative plan. If you go ahead with the work without approval, you could face expensive remedial work in the future, as retrospective agreements are not guaranteed to be approved.
When did build-over agreements come into force?
Build-over agreements came into force in October 2011 when water companies were awarded previously private areas of the sewer network. This means that if you had an extension, conservatory or other structure built over a sewer prior to October 2011, you didn’t require a build-over agreement.
However, you should still have had sign-off from Building Control for any building work over a sewer.
Do you need assistance?
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