Surbiton trunk mains project

We’ve been working to install a new trunk main on the A24. This is a £15m major infrastructure investment to reduce supply interruption and improve water supply. The replacement pipe covers 2.4km along the A24 and is a major part of our clean water network.

We’ll soon be completing the final sections of the trunk main. This involves installing valves and fittings to connect the main to our network.

We’ve had some recent challenges around pressure-testing the new main. We've designed and installed bespoke valves and fittings to overcome this. As a result, we've had to amend the works programme. Our works are on schedule despite this, so we still expect to complete the scheme in July 2025.

We appreciate that these works have been disruptive. We apologise for any additional inconvenience caused by the change of programme.

This page was last updated on 20 June 2025.

When and where we’ll be working

Our working hours will be Monday to Friday, 7am to 6pm and weekends 8am to 5pm.

These junctions on the A24 will close as part of the approved traffic management plan:

Street name	Start of closure	End of closure
Derinton Road	25 April 2025	26 June 2025
Lessingham Avenue	25 April 2025	26 June 2025
Ansell Road	25 April 2025	26 June 2025
Balham Park Road	7 January 2025	9 July 2025
Trevelyan Road	13 May 2025	23 July 2025

How this may affect you

We'll continue the connection process at the Balham Park Road junction with Balham High Road. This is the most disruptive of the connection locations on the A24. This is because it's the primary connection site, where all the testing will take place from. This closure of the junction with the A24 will be extended until 9 July 2025.
The junctions of Derinton Road, Ansell Road and Lessingham Avenue will stay closed until 8 June 2025
Our next phase will take place near the junctions of Trevelyan Road and Carlwell Street on the A24. Trevelyan Road junction will be closed until 9 July 2025. We've previously been in this location in 2024 to install the new pipes. We must now complete the connections and commission the pipes into the network.
The final phase of work will take place near the junction with Garratt Lane. A lane closure, with two-way traffic maintained at all times, will be in operation for this phase. This starts on 10 July 2025 for two weeks.
Access will be maintained for residents and businesses via diversion routes
No bus routes are being diverted as a result of these works.
You may notice an increase in noise and vehicle movements. We’ll do everything we can to keep this to a minimum by installing sound barriers, where necessary.

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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