Surbiton trunk mains project
Our upcoming work is expected to be disruptive. We're sorry for any inconvenience this causes.
We're carrying out a £15 million upgrade of our clean water main along the A24. This project is part of our wider work to strengthen and modernise the water network in South London. The next stages of the project have not yet been fully completed due to a number of challenges. This means we'll now have to return to site to complete these works.
We appreciate that this extension to the scheme will be disruptive. We apologise for any extra inconvenience caused by the extension of the programme.
Work began in July 2024. By December 2024, we had installed a new lining inside 2.34 km of the existing 30-inch trunk main. “Slip lining” means inserting a new pipe inside the old one, which strengthens it and helps prevent future leaks or bursts. This section was completed about three months ahead of schedule.
This page was last updated on 12 June 2026.
Next steps
Our next phase of work starts on 22 June 2026 at the junctions with Beechcroft Road and Brudenell Road. There'll be temporary traffic lights in place on the A24 during this time.
This complex scheme began in 2024, in collaboration with Wandsworth Council and Transport for London. Working together, we aim to reduce disruption in the area.
We know this work disrupts the community, and we’re sorry for any trouble it causes.
How you'll be affected
- Temporary two-way traffic lights will be in place on the southbound carriageway from 22 June 2026
- During the first week, the junctions with Beechcroft Road and Brudenell Road will be closed
- After this, works will move to Totterdown Street and Gatton Road. These junctions will be closed from 30 June to 7 July 2026
- The final phase will run from 8 July to 24 July 2026, with closures at Ansell Road, Derinton Road and Lessingham Avenue
- Access will be maintained for residents and businesses via diversion routes
- Bus routes will not be affected
- You may notice an increase in noise and traffic. We’ll do everything we can to keep this to a minimum by installing sound barriers, where necessary
Please see the table below for the updated junction closures of works along the A24.
Working hours
Our working hours will be Monday to Friday, 7am to 6pm. Weekends 8am to 5pm.
|
Street name |
Start of closure |
End of closure |
|---|---|---|
|
Trevelyan Road | 1 June 2026 | 21 June 2026 |
|
Carlwell Street | 1 June 2026 | 21 June 2026 |
|
Longley Road | 1 June 2026 | 21 June 2026 |
|
Beechcroft Road | 22 June 2026 | 29 June 2026 |
|
Brudenell Road | 22 June 2026 | 29 June 2026 |
|
Totterdown Street | 30 June 2026 | 7 July 2026 |
|
Gatton Road | 30 June 2026 | 7 July 2026 |
|
Ansell Road | 8 July 2026 | 24 July 2026 |
|
Derinton Road | 8 July 2026 | 24 July 2026 |
|
Lessingham Avenue | 8 July 2026 | 24 July 2026 |
Challenges
Since January 2025, our teams have focused on connecting the newly lined pipe into the existing water network. One of the most important tasks was to join it to a larger 42-inch pipe at Balham Park Road. During preparation, we found that the pipe was surrounded by a large block of concrete. This meant we couldn’t connect it at the planned spot where we had permission to manage traffic. When we tried digging at another point, we found phone and internet cables encased in concrete too. Diverting these cables would have caused major delays to the scheme.
After discussions with our design experts and operational teams, we found an alternative solution. However, this change required us to redesign our plans, carry out new checks, and get fresh approvals. This all added approximately three months to the overall programme.
The Balham connection was completed in May 2025. However, we still need to fit a special valve and chamber. This will help to control how water flows through the network and direct supply where it’s needed. Because this valve wasn’t in our original plan, it had to be custom-made, which takes time. This will be after our current traffic permits expire, so we will need to return in the new year to finish the work.
Testing
After the connection activity, we needed to test the new section of pipe. “Pressure testing” means we pump water through the pipe at a much higher pressure than normal. This makes sure there are no weak points or leaks.
In June, our team carried out the pressure tests but they didn't pass at first. This isn't unusual. The test pressure is more than three times what the pipe will experience in normal daily use. It shows us where any tiny leaks are so we can repair them before the pipe goes live.
In this area, leak detection had to be done in the early hours of the morning. This avoids road traffic and the underground trains running beneath the route. Once the leaks were found, we needed emergency permission from TfL and Wandsworth Council to dig up the road and repair them. This added more time to the programme. The final pressure test passed successfully on 1 July 2025.
Other works in the area
Other major works on the A23 at Streatham Hill in July meant we needed to demobilise our works on the A24. This was to reduce disruption and impact on traffic.
Get in touch
If you have any questions, call us on 0800 316 9800 or email customer.feedback@thameswater.co.uk. Quote number: BB70085755.
For business customers, please contact your retailer for information relating to our work.
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