Underground Water Mains Leak Detection in Copthorne

Symptoms

The water authority raised concern over unusually high water usage at a property in Crawley, RH10, and suspected a leak on the pipework. A trace was required to establish exactly where the leak was occurring before any repair work could be planned.

On arrival, the water meter was observed to be passing water at a steady rate despite no water being used inside the property. When the internal stopcock was isolated, the meter continued to register flow, which confirmed the leak was not on any internal pipework but on the underground supply between the water meter on the communal pathway and the internal stopcock in the kitchen.

This kind of situation calls for a structured water mains leak detection approach — isolating sections of the supply, pressure testing to rule out internal faults, and then deploying specialist equipment to pinpoint the leak underground without unnecessary excavation.

Methods Used

With the leak confirmed to be on the underground section of pipework, pressure testing was carried out first to formally rule out any internal leaks before attention turned to the ground. Once internal pipework was cleared, tracer gas was introduced into the supply pipe and tracing equipment was used to follow the gas as it escaped at the leak point, narrowing the location to an area of underground pipework running beneath the concrete pathway.

Acoustic correlation was then applied to the indicated area to confirm the precise point before any concrete was broken. This combination of methods — standard practice in water mains leak detection — meant excavation was kept to a minimum, with the path only opened at the confirmed leak location.

Investigation Process

1. 1
   Water meter monitored

   On arrival, the water meter was observed passing water at a steady rate with no water in use inside the property, indicating a leak was present on the supply pipework.

2. 2
   Internal stopcock isolated

   The internal stopcock was closed and the meter was monitored again. Flow continued through the meter, confirming the leak was on the underground section between the meter and the stopcock.

3. 3
   Pressure testing completed

   Pressure testing was carried out on the internal pipework and returned no faults, ruling out any internal leaks and confirming the underground supply as the source.

4. 4
   Tracer gas introduced

   Tracer gas was introduced into the pipework and tracing equipment was used to follow the escape point, locating the leak on the underground pipework beneath the concrete pathway.

5. 5
   Acoustic correlation applied

   Sound acoustics were used to confirm the indicated area, pinpointing the precise location of the leak before any ground was opened.

6. 6
   Concrete pathway excavated

   A section of the concrete path was removed to expose the underground pipework, where a damaged section of copper pipe was visually identified as the source of the leak.

7. 7
   Pipework repaired and area reinstated

   The damaged copper section was replaced with new 25mm blue poly pipe and new fittings. The exposed area was then backfilled.

Result & Outcome

The leak was found on a damaged section of copper pipework running underground beneath the concrete pathway, between the water meter on the communal pathway and the internal stopcock in the kitchen. The combination of tracer gas and acoustic correlation allowed the exact point to be confirmed before any excavation, limiting the concrete removal to only the area directly above the fault.

Once exposed, the damaged copper pipework was replaced with a new 25mm blue poly pipe section, installed with new fittings. The excavated area was backfilled on completion. The repair addresses the source of the elevated water usage flagged by the water authority.

For a water mains leak detection job of this type — an underground supply running beneath a hard surface with no visible signs above ground — tracer gas combined with acoustic confirmation is the most reliable approach to minimise unnecessary disruption while ensuring an accurate result.