Underground Water Mains Leak Detection in Teddington

Symptoms

A property in HP11 had a confirmed failure on its incoming mains supply, requiring further trace and access work to pinpoint the exact route and condition of the pipework. The mains supply ran beneath a concrete screed floor, and the precise path of the pipe through the building was unknown — making any targeted excavation or repair work impossible without additional investigation.

The situation called for water mains leak detection work that went beyond a standard survey. The pipe route needed to be established accurately before any repair could be assessed or carried out, and the area of concern extended beneath an internal floor with laminate and screed covering the pipework.

Methods Used

The investigation combined multiple techniques to establish the precise route of the incoming mains supply beneath the floor. Initial access was made in the corner of the lounge, where laminate flooring and screed were removed.

A tracing cable was fed into the supply and a CAT and Genny test was conducted, which established the pipe ran toward the kitchen wall but the signal was lost approximately three feet from the party wall — suggesting a change in direction or depth.

Ground penetrating radar was then deployed to continue tracking the pipe beyond the point where the tracing cable signal ended. This confirmed the mains supply angled sharply into the corner directly beneath the electrical consumer unit.

In water mains leak detection work of this nature, combining tracer cable with ground penetrating radar is often the only reliable way to map a supply that deviates unexpectedly beneath a solid floor. Further screed was removed below the consumer unit and excavation reached approximately one metre depth before the incoming 20mm black poly supply was exposed.

Investigation Process

1. 1
   Floor access in lounge corner

   Laminate flooring and screed were removed in the corner of the lounge to begin exposing the incoming mains supply and allow tracing equipment to be introduced.

2. 2
   Tracing cable and CAT and Genny test

   A tracing cable was run into the mains supply and a CAT and Genny test was carried out. The cable signal tracked the pipe to approximately three feet from the party wall, at the edge of the kitchen wall, before the signal could not be followed further.

3. 3
   Ground penetrating radar survey

   GPR was used to continue mapping the pipe route beyond where the tracing signal ended. The radar confirmed the mains supply continued along the same general area before angling sharply into the corner directly beneath the electrical consumer unit.

4. 4
   Excavation beneath consumer unit

   Screed was removed below the consumer unit and excavation was carried out to a depth of approximately one metre, eventually exposing the incoming 20mm black poly mains supply.

5. 5
   New mains riser installed and connected

   A new 20mm blue poly mains riser was run from the newly installed internal stopcock and 15mm copper internal mains supply into the existing 20mm black poly supply, just in front of the external wall and external water meter, with appropriate adaptors fitted.

6. 6
   Pressure test and completion

   The repaired mains supply was tested using 4.0 bar of compressed air with no pressure drop recorded, confirming the installation was sound. The report was prepared for submission to the customer's insurers.

Result & Outcome

The incoming 20mm black poly mains supply was located at approximately one metre depth in the corner of the lounge, directly beneath the electrical consumer unit — a position that had not been apparent from initial access and could only be confirmed by combining tracing cable work with ground penetrating radar. The pipe route had deviated sharply from its expected path, which is precisely why this level of water mains leak detection investigation was necessary before any repair could be planned.

A new 20mm blue poly mains riser was installed from the internal stopcock back to the existing black poly supply just inside the external wall, with the joint made just in front of the external water meter. Pressure testing at 4.0 bar of compressed air confirmed no drop in pressure and the supply was restored satisfactorily.

With the investigation and repair complete, the findings have been documented for submission to the customer's insurers, providing a clear technical record of the pipe route, the excavation required, the materials used, and the pressure test results.