Underground Water Mains Leak Detection in East Dereham

Symptoms

The internal stopcock was found inside the kitchen sink unit, next to the water softener. The external main pipework ran approximately 20 metres in total, including a section beneath an extension, making direct visual inspection impossible.

There was no visible evidence of the leak at surface level — no wet patches, no lifted flags, no obvious signs of where water was escaping.

Methods Used

This combination of methods is standard practice in water mains leak detection when no surface evidence exists and the pipe runs beneath hard landscaping. Each stage reduced the area of uncertainty before any excavation was attempted, meaning digging was confined to the precise location rather than a broad exploratory trench.

Investigation Process

1. 1
   Pressure test on external main

   The internal stopcock was removed and the pressure test kit was connected directly to the external main pipework. The test confirmed a leak was present somewhere on the external supply.

2. 2
   Tracer gas investigation

   Tracer gas was introduced into the isolated pipework and a gas detector was used to survey the ground surface. The detector identified the leak location in the area next to the drainage manhole.

3. 3
   Acoustic pinpointing

   Acoustic equipment was deployed at the indicated zone to pinpoint the exact leak position before any excavation began.

4. 4
   Customer informed

   The customer was briefed on the findings — the suspected leak location and the proposed solution — before any digging took place.

5. 5
   Excavation of driveway

   Driveway blocks were lifted and the ground was excavated at the pinpointed location to expose the pipework.

6. 6
   Leak identified and assessed

   One leak was found on the 25mm black poly pipe. The pipe had cracked where it ran alongside the concrete wall of the drainage manhole.

7. 7
   Pipe section replaced

   The cracked section of pipework was cut out and replaced using Philmac fittings and inserts with new 25mm MDPE pipe.

8. 8
   Retest passed

   A pressure retest was carried out on the repaired pipework and passed, confirming no further leaks were present.

9. 9
   Reinstatement and restoration

   The excavated area was backfilled, the driveway blocks were relaid, and water pressure was restored throughout the property.

Result & Outcome

For a water mains leak detection job of this type — an underground pipe with no surface evidence and a complex route beneath hard landscaping — the staged approach meant that the cause of a 300-litre-per-day loss was accurately located and resolved in a single visit without unnecessary excavation.