Sewer adoption technical submission
Drainage design and drawings for new sewers to be adopted by the water company under Section 104.
About this service
When a development needs new sewers that will serve several properties, it often makes sense for the sewerage company to adopt them. Once adopted, the company owns and maintains the sewers, rather than the homeowners or a management company. The usual route is an agreement under Section 104 of the Water Industry Act 1991. To get there, the developer must submit a design that meets the company's adoption standards, and the company must approve it before construction starts.
We prepare Section 104 technical submissions for residential and mixed-use developments in London, where the sewerage company is usually Thames Water. The submission includes the sewer layout, long sections, manhole details, hydraulic calculations and construction details, all prepared to the national design and construction guidance for adoptable sewers. We also submit it, respond to technical queries and revise the design until it is approved.
A Section 104 design usually builds on an approved foul drainage strategy and surface water strategy. Where new sewers will run close to or beneath buildings, the design must also respect easements. Every submission goes through our three-step quality control process, with final sign-off by our Head of Engineering, before it reaches the water company, which helps cut down repeated rounds of comments.
When you need it
- You're building new sewers that will be adopted
- The water company needs a technical submission
What's included
- Sewer design to adoption standards
- Drawings and calculations
- Submission to the water company
How it works
- Confirm adoption scopeWe review the site layout and drainage strategy, decide which sewers are suitable for adoption and confirm the connection points and any capacity conditions from the sewerage company.
- Design to adoption standardsWe design gravity sewers, manholes and any pumping arrangements to the adoption guidance, checking gradients, depths, self-cleansing velocities, pipe materials and safe access for future maintenance by the sewerage company.
- Prepare drawings and calculationsWe produce layout plans, long sections, standard details and hydraulic calculations, coordinated with roads, foundations, trees and other utilities so the sewers can be built and maintained without conflicts.
- Submit and respondWe submit the technical package to the sewerage company, answer their comments and issue revised drawings and calculations as needed until technical approval is granted for the scheme.
- Support constructionWe remain available to answer contractor questions and coordinate any design changes needed on site, so the sewers can be inspected, completed and progress towards adoption.
What you receive
Planning ahead for adoption
Adoption takes time. Technical review, the legal agreement and the bond or security the sewerage company requires all need to be in place before work starts, so building the Section 104 process into the programme early avoids delays. Once the sewers are built and inspected, there is usually a maintenance period before the company formally takes them over. Your contractor will need to follow the approved design closely.
Layout decisions made at planning stage can make adoption easy or hard. Sewers under private gardens, too close to foundations or beneath buildings are often not acceptable for adoption, and pumping stations bring extra requirements. Where an existing public sewer crosses the site, a build over or near sewer package may be needed instead of, or as well as, a Section 104 agreement. Our guide to building over a public sewer explains the difference.
Frequently asked questions
What is a Section 104 agreement?
It is an agreement between a developer and a sewerage company under Section 104 of the Water Industry Act 1991, for new sewers to be adopted once they are built to an approved standard. The developer submits a technical design, provides a bond or security, builds the sewers under inspection and, after a maintenance period, the company takes ownership and responsibility for them.
Do new sewers on a small development have to be adopted?
Not always. Private drains serving a single property usually remain private. Where a new sewer serves several homes, adoption is often the sensible choice because it gives owners certainty about future maintenance, and many water companies expect new shared sewers to be built to adoptable standards. Whether a Section 104 is right for your scheme depends on the layout, so seek advice early.
How long does Section 104 technical approval take?
It varies with the sewerage company's workload and the quality of the submission. A complete, well-coordinated design avoids repeated rounds of comments, which is the main cause of delay. Allow time in the programme for technical review, the legal agreement and the bond before construction. We prepare our design efficiently, with a typical turnaround of 10 working days for the initial submission package.
What is the difference between Section 104 and Section 106?
Section 104 deals with adopting new sewers built by a developer, so the sewerage company takes ownership once they are complete. Section 106 of the Water Industry Act deals with the right to connect a drain or sewer to the existing public network. Many developments need both: a Section 106 application for the connection and a Section 104 agreement for the new sewers.