Underground Water Mains Leak Detection in Falmouth

Symptoms

The property in TR2 is a detached residence with a water meter situated in the rear garden and pipework extending from the main supply down to a garage at the front. A leak had developed somewhere along the external pipework, though its exact location was not immediately apparent given the layout of the site and the fact that sections of pipe are buried within concrete.

The challenge on this job was that the pipework routes beneath the patio and around the structure, making direct visual inspection impossible without excavation. Establishing precisely where the fault lay before any ground was broken was essential to avoid unnecessary disruption to the property.

A water mains leak detection investigation of this nature — involving buried pipework, concrete encasement, and a complex pipe route — requires a combination of methods to narrow down and then pinpoint the leak site with confidence.

Methods Used

The investigation began with stopcock isolation to establish that the leak was external, ruling out internal plumbing as a source. Acoustic leak detection equipment was then used to scan the buried pipework, producing readings that initially pointed to an area along the side of the annex.

Tracer gas was introduced at the garage — the furthest point from the main supply — and the system was pressure tested at 3 bar for 30 minutes, during which a steady pressure drop confirmed an active leak.

With tracer gas still present in the system, a gas sniffer was used to walk the pipe route systematically. The acoustic readings near the garage did not correspond to any gas presence at ground level, but gas was detected near the kitchen window and found to be entering the kitchen from beneath the suspended floor.

A tracer cable inserted through the internal stopcock location mapped the pipe route and identified a fitting approximately 1.2 metres along; an endoscope camera provided visual confirmation of the fitting before any excavation took place. This layered approach is characteristic of thorough water mains leak detection on complex buried systems.

Investigation Process

1. 1
   Stopcock isolation

   On arrival, the stopcock in the garage and the main internal stopcock were both isolated. This confirmed the leak was on the external pipework, not within the property.

2. 2
   Acoustic detection deployed

   Acoustic leak detection equipment was used along the buried pipework. Readings indicated a potential leak area along the side of the annex, where the pipe is encased in concrete.

3. 3
   Tracer gas introduced and pressure test conducted

   Tracer gas was introduced at the garage connection point — the furthest point from the main supply. The system was then pressure tested at 3 bar for 30 minutes, and a steady pressure drop confirmed the presence of an active leak.

4. 4
   Gas sniffer survey

   With tracer gas active, a gas sniffer was used to survey the pipe route. No gas was detected near the garage area where the acoustic readings had pointed, but gas was found near the kitchen window and was also present inside the kitchen, rising from beneath the suspended floor.

5. 5
   Tracer cable and endoscope investigation

   The internal stopcock was removed and a tracer cable was inserted to map the pipe's route. A fitting was identified approximately 1.2 metres along, and its presence was visually confirmed using an endoscope camera.

6. 6
   Patio excavated and fitting exposed

   With the customer's permission, an area of patio outside the kitchen was carefully excavated. The fitting identified was found to be a tee that had failed due to root ingress from nearby vegetation.

7. 7
   Repair completed

   The faulty 20mm tee fitting was removed and replaced with a new, compliant fitting.

Result & Outcome

The leak was located beneath the patio outside the kitchen, approximately 1.2 metres from the internal stopcock position. The cause was a failed 20mm tee fitting whose failure was attributed to root ingress from nearby vegetation. Despite acoustic readings initially suggesting the annex side as the likely area, the tracer gas survey redirected the investigation to the kitchen side of the building, demonstrating how multiple methods working in combination are essential on jobs where pipe routes are not straightforward.

The endoscope camera provided visual confirmation of the fitting's position before any ground was broken, meaning excavation was targeted and limited to the area where the fault actually lay. The faulty tee was removed and replaced with a compliant fitting, resolving the leak.

For water mains leak detection cases involving pipework buried beneath hard landscaping, this outcome illustrates the value of precise pinpointing before excavation. The customer has been advised to contact their buildings insurer regarding Trace and Access cover, and to monitor for any future signs of damp or water ingress given the age of the pipework in the area.