Underground Water Mains Leak Detection in Cricklade

Symptoms

A property in SN15 was experiencing an active water leak that had become visible at the surface. Water was escaping from the tarmac near the front of the property, and the surrounding area was noticeably damp on arrival.

The main water valve at the footpath had already been shut off prior to the engineer attending, indicating the situation had been identified as serious enough to isolate the supply.

The leak was originating from an underground water supply pipe running beneath the tarmac surface. This type of subsurface mains leak can go undetected for some time before breaking through to the surface, and by the point of visible escape, water loss and ground saturation are typically already significant.

A water mains leak detection job of this nature — where water is visibly surfacing near a mains supply route — requires methodical investigation to confirm the precise leak point before any excavation is carried out, minimising unnecessary disruption to the surface.

Methods Used

The investigation began by reactivating the main water valve at the footpath, which had been shut off before arrival. Within approximately three minutes of restoring the supply, water was observed escaping from the edge of the tarmac — confirming an active leak and providing a focal area for further testing.

An acoustic listening device was then deployed across the tarmac surface to pinpoint the exact leak location beneath, identifying a strong signal consistent with a pressurised leak on the buried pipe.

This approach — combining a controlled supply reinstatement with acoustic detection — is standard practice in water mains leak detection and allowed the leak point to be confirmed with sufficient precision before the tarmac was lifted. Excavation was then performed in a targeted manner based on the acoustic findings, exposing the damaged section of a 25mm metal water supply pipe.

Investigation Process

1. 1
   Arrival and Initial Observations

   On arrival, water was observed escaping from the tarmac surface near the front of the property, with the surrounding ground heavily saturated. The main water valve at the footpath was confirmed as isolated.

2. 2
   Water Supply Reinstated

   The main valve at the footpath was reactivated to restore pressure to the pipe. Within approximately three minutes, water was seen escaping from the edge of the tarmac surface.

3. 3
   Acoustic Detection Performed

   An acoustic listening device was deployed across the tarmac area. A strong leak signal was identified beneath the surface, confirming the location of the leak on the buried pipe.

4. 4
   Tarmac Removed and Excavation Carried Out

   The tarmac was carefully lifted and an excavation was performed at the identified location, exposing a leak on a 25mm metal water supply pipe.

5. 5
   Pipe Repaired

   The damaged section of pipe was repaired using two universal fittings (21/27/25mm) and a section of 25mm MDPE pipe to replace the compromised portion.

6. 6
   Pressure Test Conducted

   A pressure test was carried out following the repair, confirming no further leaks were present in the water supply system.

7. 7
   Reinstatement Completed

   The excavated area was backfilled and the tarmac surface was reinstated to its original condition, completing the job.

Result & Outcome

The leak was located beneath the tarmac surface near the front of the property, on a 25mm metal water supply pipe. The acoustic listening device identified a strong and clear signal at the leak point, allowing excavation to be carried out precisely without unnecessary surface disruption. The damaged section of pipe was repaired using two universal fittings (21/27/25mm) and 25mm MDPE pipe.

A pressure test conducted after the repair confirmed the water supply system was fully sealed with no further leaks present. The excavation was backfilled and the tarmac reinstated, leaving the site in its original condition. For a water mains leak detection job involving a buried metal supply pipe, this outcome — acoustic pinpointing followed by targeted excavation and same-visit repair — is the most efficient resolution path and avoids speculative digging.

The customer is advised to contact their building insurer, as the costs associated with this type of job are commonly covered under Trace and Access provisions on standard home insurance policies. No further works are currently recommended.