Underground Water Mains Leak Detection in Bexleyheath

Symptoms

When the engineer arrived and conducted a meter test, the live leak rate measured 60 litres per hour — well above the reported figure. Visible pooling of water was noted close to the water meter and property boundary, while the surrounding pavement remained completely dry.

This localised saturation was an early indicator that the leak origin was near the boundary. Water mains leak detection work of this kind, where the reported rate and the measured rate differ significantly, often points to a developing fault that has worsened since the initial report.

Methods Used

Tracer gas reached the leak area within five minutes of introduction and was detected in the lawn adjacent to the property boundary, on the opposite side of the boundary wall from the external meter. The area was excavated to expose the pipework.

This revealed a lead pipe running under the boundary wall and connecting to a 15mm mains copper pipe — a common configuration in older properties. A leak was confirmed on the lead section.

Following the repair, a retest identified a further leak on the pipe outside the property boundary, which falls under the water company's responsibility.

Investigation Process

1. 1
   Meter test on arrival

   A flow meter test was carried out immediately on arrival. This recorded a live leak rate of 60 litres per hour, higher than the 22 litres per hour figure reported by the water company.

2. 2
   Visual observation of pooling

   Excess water was noted close to the water meter and property boundary. The surrounding pavement was dry, focusing attention on the boundary area as the likely leak zone.

3. 3
   Pressure testing

   Pressure testing was carried out on the supply system to confirm an active loss and establish baseline conditions before tracer gas introduction.

4. 4
   Tracer gas introduced

   Hydrogen tracer gas was introduced into the water supply system. The gas reached the leak area within five minutes.

5. 5
   Gas detected in lawn

   Tracer gas was detected in the lawn adjacent to the property boundary, on the opposite side of the boundary wall from the external meter, identifying the precise area for excavation.

6. 6
   Excavation and pipe inspection

   The lawn area was excavated to expose the water pipe. A lead pipe was found running under the boundary wall and connecting to a 15mm mains copper pipe. The leak was confirmed on the lead section.

7. 7
   Lead pipe replaced

   The lead pipe was replaced up to the property boundary using 20mm MDPE blue water mains pipe, connected with two Universal Transition Couplings.

8. 8
   Retest and further leak identified

   Following the repair, the system was retested. A further leak was indicated on the pipe outside the property boundary. The customer was advised to contact the water company to carry out the repair on the external section.

Result & Outcome

The combination of flow metering, tracer gas, and targeted excavation meant the fault was located and repaired without unnecessary disruption. The measured leak rate of 60 litres per hour has been eliminated on the customer's section of pipe, and the outstanding external leak has been formally flagged to the water company.