Internal Cold Mains Leak Detection in Cosham

Symptoms

A property in PO6 had a suspected leak on the internal main water supply. There was no visible water present, but damage to a wall in the conservatory indicated that moisture had been affecting the structure.

The absence of visible water made the source difficult to pinpoint without specialist internal leak detection equipment.

Adding to the complexity, the internal stop valve — located beneath the stairs — had been installed incorrectly by a previous plumber using copper pipework in a section where regulations prohibit its use before a lead pipe. This non-compliant installation needed to be addressed before any meaningful pressure testing or acoustic investigation could take place.

Internal leak detection cases like this, where the pipework runs beneath floors and behind walls, require a methodical approach. The lack of surface water and the involvement of older lead pipework meant the investigation needed to progress from acoustic detection through to tracer gas before the source could be confirmed.

Methods Used

Before testing could begin, the non-compliant copper stop valve beneath the stairs was replaced with a 25mm Plasson plastic stop valve, bringing the installation in line with clean water regulations and providing a reliable isolation point for the investigation. A compressor was then connected and acoustic leak detection equipment deployed, which picked up noise in the conservatory area.

To narrow the location further, tracer gas was introduced into the pipework and gas detection equipment used to trace the signal. Positive gas readings were located beneath the kitchen floor, directing the physical investigation to that specific area.

This combination of acoustic and tracer gas methods is standard practice in internal leak detection work involving concealed lead pipework, and on this job it allowed the leak to be pinpointed before any unnecessary opening up of the structure.

Investigation Process

1. 1
   Stop valve replaced

   The existing internal stop valve beneath the stairs was found to have been installed incorrectly using copper pipework ahead of a lead pipe, contrary to clean water regulations. It was replaced with a compliant 25mm Plasson plastic stop valve.

2. 2
   Acoustic detection carried out

   A compressor and acoustic leak detection equipment were connected to the internal supply. Noise was detected in the conservatory area, indicating a leak within that part of the building.

3. 3
   Tracer gas deployed

   Tracer gas was introduced into the pipework and a gas detector used to trace the signal. Positive readings were located beneath the kitchen floor, confirming that as the leak site.

4. 4
   Floor opened up

   Skirting boards, floor panels, and floorboards were removed to expose the pipework beneath the kitchen floor.

5. 5
   Leak found and repaired

   A leak was found on a lead tee junction beneath the kitchen floor. At the customer's request, two lead tee junctions were removed and replaced with 25mm MDPE plastic pipework and fittings, including equal tee junctions, straight couplings, rubber adapters, and a stop valve.

6. 6
   System tested and reinstated

   The repaired system was pressure tested and confirmed leak-free with no further leaks on the internal main water supply. Floorboards and laminate flooring were reinstated, and the site left clean and tidy.

Result & Outcome

The leak was found on a lead tee junction beneath the kitchen floor, identified precisely using tracer gas after acoustic detection had narrowed the search to the conservatory and kitchen area. Two lead tee junctions were removed in total and replaced with plastic pipework and fittings — 25mm MDPE pipe, equal tee junctions, straight couplings, rubber adapters, and a stop valve — completing the repair in a single visit.

Following the repair, the system was pressure tested and confirmed to be fully leak-free. No further leaks were identified on the internal main water supply. Floorboards and laminate flooring were reinstated before the job was closed out.

For internal leak detection work involving older lead pipework, this outcome is a clean resolution: the source was confirmed instrumentally before any unnecessary opening up of the structure, and the non-compliant copper stop valve installation was also corrected as part of the same visit, leaving the supply in a compliant and serviceable condition.