Underground Water Mains Leak Detection in Liverpool

Symptoms

The owner of a property in L25 had received a notification from his water supply company indicating a leak on his property. On arrival, the customer pointed out visible water damage to the walls in the garage and the adjacent kitchen wall, which had been caused by the ongoing leak.

The internal stopcock was found to be non-functional — when operated, water continued to flow through, meaning the supply could not be isolated in the usual way.

A water mains leak detection visit was arranged to locate the source of the leak precisely before any repair work could be planned. The external water mains meter was checked and showed significant movement on the micro dial even with no deliberate water use, confirming an active leak on the property.

The combination of meter movement, visible wall damage, and a faulty stopcock pointed to a hidden leak somewhere within the garage.

Methods Used

The investigation began at the external water mains meter, where movement on the micro dial confirmed the presence of an active leak. Because the internal stopcock could not isolate the supply, the engineer could not use a simple flow-off comparison and instead moved directly to specialist detection methods.

Tracer gas was introduced via a tap in the garage and the area was systematically inspected; gas was detected in the garage, narrowing the search to that zone. Acoustic equipment was then deployed to listen for water movement within the structure, and water escape was detected in the garage, consistent with the tracer gas findings.

With the leak zone confirmed, the engineer excavated the concrete floor and ground in the garage with the customer's permission to expose the pipework. This combination of tracer gas and acoustic correlation is the standard approach for water mains leak detection where the pipe runs beneath a solid floor and no surface sign of the leak is visible.

Investigation Process

1. 1
   Meter inspection

   The external water mains meter was inspected and showed major movement on the micro dial, confirming an active leak on the property.

2. 2
   Stopcock assessment

   The internal stopcock was operated but could not isolate the supply — water continued to run through, preventing a flow-off test.

3. 3
   Tracer gas test

   Tracer gas was introduced via the tap in the garage and the property was inspected; gas was detected in the garage, indicating the leak was located in that area.

4. 4
   Acoustic detection

   Acoustic equipment was used to check for water movement beneath the structure; water escape was confirmed in the garage, consistent with the tracer gas findings.

5. 5
   Excavation

   With the customer's permission, the concrete floor and ground in the garage were excavated to expose the pipework and access the source of the leak.

6. 6
   Leak identified

   The copper pipe was found to be in poor condition; the leg running from the main copper pipe to the garage tap had snapped off, allowing water to escape freely.

7. 7
   Temporary repair carried out

   With the customer's permission, the damaged section was repaired using plastic fittings and pipe — a temporary fix to stop the leak while a full pipe replacement is planned.

Result & Outcome

The leak was located beneath the concrete floor of the garage. Excavation revealed that the copper pipe leg running from the main supply pipe to the garage tap had snapped off at the connection point, creating an unrestricted escape of water. This explained the extent of the water damage observed on the garage walls and the adjacent kitchen wall.

A temporary repair was completed using plastic push-fit fittings and pipe to restore the supply and stop the active leak. As is common in water mains leak detection cases involving older copper pipework, the repair is described as temporary — the copper pipe is in poor overall condition and will require a full replacement with 25mm MDPE blue plastic pipe in the near future. The customer also needs to allow the ground to settle before the concrete floor can be reinstated.

Several additional issues were identified that require attention: the internal stopcock must be replaced as it cannot isolate; the downstairs toilet filling and flushing valves need replacing as the toilet is taking on water continuously; and a drying and restoration programme will be needed to address the sustained water damage to the garage and kitchen walls.