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NRV Carriageway
Installation
The Problem
The property was experiencing recurring drainage backflow from the public sewer network, resulting in repeated flooding risk.
Client
Water Board
Property Type:
Residential House
Location:
Shepherd’s Bush, London
The Assessment
Our team carried out a full inspection, which included:
- CCTV surveying of the drainage system
- Dye testing of laterals and pipe connections
- Taking detailed measurements of the property drainage and the public sewer in the carriageway
- Sonde tracing and marking the route of the drain from the property to the main sewer
- Producing a detailed report identifying faults, restrictions, and installation constraints
The Solution
Due to the depth required (approximately 4 metres) and the lack of space within the
property boundary, it was determined that the most effective long-term solution was to
excavate a shaft within the carriageway to install a non-return valve. This ensured safe
access to the sewer and reliable prevention of future backflow.
Key Steps
1. Obtaining permits and completing site setup and traffic management.
2. CAT scanning the excavation area and clearly marking existing services.
3. Excavating to a safe depth and installing ground support before continuing excavation.
4. Securing identified services, forming the excavation base, and preparing for the chamber
installation.
5. Gas monitoring of the confined space and installation of the non-return valve.
6. Constructing the new chamber, reinstating the excavation, and resurfacing the carriageway with tarmac.
The Result
The non-return valve was inspected and tested to confirm correct opening and closing.
Associated pipework was checked to ensure there were no snagging points or restrictions.
The installation successfully eliminated sewer backflow, with no further issues reported.
Positive feedback was received from the client, homeowner, and local authority.
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