Internal Cold Mains Leak Detection in Carlisle

Symptoms

The property in CA4 is a two-storey dwelling that had developed a mains water leak. At the point of booking, it was unclear whether the source was internal or external, so internal leak detection was required to establish this before any remedial work could be planned.

The situation was complicated by the layout of the property. The internal stopcock was located behind the toilet, making it less than straightforward to access, and there were no other isolation points for the hot or cold feeds anywhere in the property.

Without knowing the leak's location, the full extent of the problem — and what would be needed to fix it — remained unknown.

With water loss ongoing and no obvious visible source, a structured multi-method investigation was necessary to pinpoint where the failure had occurred and whether it involved one pipe or more.

Methods Used

The investigation followed a logical sequence, beginning with supply isolation to determine whether the leak was internal or external. With that confirmed as internal, pressure testing was applied to the internal mains, which failed, narrowing the search to the pipework inside the property.

Internal leak detection of this kind relies on combining multiple methods to triangulate a precise location rather than relying on any single result.

From there, tracer gas, acoustic equipment, thermal imaging, and a damp meter were all deployed in the kitchen utility area, where positive results converged. With the leak's location identified beneath the concrete floor and the customer's agreement obtained, the floor was excavated to expose the pipework directly.

This confirmed leaks on both the cold and hot feeds at that location.

Investigation Process

1. 1
   Stopcock located and accessed

   The internal stopcock was found behind the toilet. Access was gained to operate it as part of the initial isolation process.

2. 2
   Supply isolated at the meter

   The mains supply was turned off at the meter. Usage stopped immediately, confirming the leak was internal rather than external.

3. 3
   Pressure test applied to internal mains

   A pressure test was carried out on the internal mains pipework. The pipe failed the test, confirming a fault within the internal supply.

4. 4
   Tracer gas, acoustic, and damp meter tests conducted

   Tracer gas was introduced and a positive result was detected in the kitchen utility area. Acoustic testing and moisture meter readings in the same location also returned positive results, converging on a consistent leak position.

5. 5
   Thermal imaging carried out

   Thermal imaging was used across the floor area to identify temperature anomalies associated with water loss beneath the surface.

6. 6
   Concrete floor excavated

   With the customer's permission, the concrete floor in the kitchen utility area was excavated to expose the buried pipework, revealing active leaks on both the cold and hot feeds.

7. 7
   Washing machine repositioned

   The washing machine power cable was cut to allow the appliance to be moved — the kitchen unit had been fitted around it, leaving no way to remove the plug conventionally.

8. 8
   Repairs completed and service valve installed

   Two sections of pipework were cut out and replaced with new elbows, fittings, and replacement pipework. A service valve was installed on both feeds, as there were no other isolation points in the property and accessing the stopcock required removing toilet units.

9. 9
   Repair retested — all tests passed

   Following completion of the repair, the system was retested. All tests passed at the time of the visit.

Result & Outcome

The leaks were found beneath the concrete floor in the kitchen utility area, affecting both the cold and hot feeds at the same location. The convergence of tracer gas, acoustic, thermal imaging, and damp meter results before excavation meant the dig was targeted and the exposed pipework confirmed exactly what the testing had indicated.

Repairs were completed during the same visit. Two sections of pipework were removed and replaced, with new elbows, fittings, and service valves installed. The service valves were a practical addition given that — prior to this work — the property had no accessible isolation points for the hot or cold supplies other than the stopcock behind the toilet. For any future maintenance, isolation can now be achieved without dismantling bathroom furniture.

This outcome is consistent with what internal leak detection is designed to deliver: a confirmed location and a completed repair rather than an open-ended investigation. The customer was advised not to reinstate the concrete in the small excavated section so that the new service valves remain accessible, and the retest confirmed the repair was holding at the time of the visit.