Underground Water Mains Leak Detection in Bursledon

Symptoms

At a property in SO31, a continuous movement on the external water meter was noticed — a strong indicator that water was escaping somewhere in the system. To determine whether the leak was internal or external, the internal stopcock inside the downstairs toilet boxing was isolated.

After closing the stopcock, the water meter was re-checked and movement continued, pointing firmly to a leak on the external mains supply rather than the internal pipework.

With an external mains leak confirmed as the likely cause, a full water mains leak detection survey was arranged. The leak had not yet surfaced visibly, meaning the exact location on the external pipework needed to be identified before any repair work could begin.

Left unaddressed, an external mains leak of this nature will result in ongoing water loss and potential damage to surrounding ground and structures. Pinpointing the precise location was essential to keep excavation targeted and the repair straightforward.

Methods Used

The investigation began with sectional isolation to confirm the leak was external, followed by a tracer gas survey. Gas was introduced into the system through the garden hose tap and the supply was pressurised to 2 bar.

A pressure test then confirmed a consistent pressure drop, providing clear evidence of an active leak. With the gas in the system, an electronic gas sensor was used to sweep the external areas of the property systematically.

A strong tracer gas signal was detected within the hedge area, close to the water meter. This is the kind of focused result that water mains leak detection relies on — narrowing a potential leak to a specific surface point before any ground is broken.

The hedge was carefully removed to allow access, and targeted excavation of the soil beneath exposed the leak source on a black poly pipe.

Investigation Process

1. 1
   Meter Movement Observed

   On arrival, continuous movement on the external water meter was noted with no water in use, indicating an active leak somewhere in the supply.

2. 2
   Internal Stopcock Isolated

   The internal stopcock inside the downstairs toilet boxing was closed to determine whether the leak was internal or external.

3. 3
   Meter Re-checked — External Leak Confirmed

   With the stopcock isolated, the water meter was re-checked and continued to show movement, confirming the leak was on the external mains supply.

4. 4
   Tracer Gas Introduced

   Gas was introduced into the system via the garden hose tap and the supply was pressurised to 2 bar in preparation for the tracer gas survey.

5. 5
   Pressure Drop Confirmed

   A pressure test was carried out, revealing a consistent pressure drop that confirmed the presence of an active leak on the pressurised system.

6. 6
   Gas Survey of External Areas

   An electronic gas sensor was used to inspect the external areas of the property, detecting a strong tracer gas signal within the hedge area near the water meter.

7. 7
   Hedge Removed and Soil Excavated

   The hedge was carefully removed to gain access, and excavation of the soil beneath exposed the leak source on a black poly pipe.

8. 8
   Repair Completed

   The leak was repaired using 20mm MDPE fittings and pipework, restoring the integrity of the external mains supply.

Result & Outcome

The leak was located on a black poly pipe beneath the hedge area, in close proximity to the external water meter. The tracer gas survey provided a precise surface indication, meaning excavation was targeted directly at the fault rather than exploratory. This is the value of a structured water mains leak detection approach — the ground is only opened where the evidence points.

Once exposed, the leak was repaired using 20mm MDPE fittings and pipework, providing a durable fix suited to the external mains supply. The repair was completed as part of the same visit, resolving the active water loss confirmed by the meter movement on arrival.

The property owner is advised to contact the water company to notify them the leak has been located and repaired, and to continue monitoring the external meter for any further movement to ensure no secondary issues are present on the supply.