Internal Cold Mains Leak Detection in Telford

Symptoms

The occupant of a detached house in a property in TF7 noticed a damp patch appearing on the ceiling and wall in the living room. The property has an unvented hot water and heating system, with the internal stop tap located in a corner unit in the kitchen.

The visible damp was the first sign that water was escaping somewhere within the building's pipework.

Because the property has both heating and hot water circuits in addition to the cold mains supply, there were several potential sources for the leak. Establishing which system was affected — and precisely where — required a methodical process of isolation and testing.

This is exactly the kind of job where internal leak detection is needed: the symptom is visible, but the source is hidden.

Without pinpointing the leak accurately, any repair attempt risks opening up unnecessary areas of the property or missing the fault entirely. A structured detection approach was the only reliable way to identify the damaged section of pipe.

Methods Used

The investigation began with isolation of the internal stop tap and a full drain-down of the system. Pressure testing equipment was connected to the cold mains supply, and the pipework was pressurised to 1.5 bar.

After 15 minutes, a drop of 0.1 bar was recorded. The heating system was then isolated and the test repeated — pressure continued to fall.

The hot water system was isolated next, but the pressure drop persisted, confirming the fault lay on the cold feed rather than in either of the other circuits.

Tracer gas was introduced to attempt to pinpoint the leak, but the leak rate was too high for that method to produce a reliable result. Acoustic testing was carried out instead and produced a positive signal, directing attention to a specific area of the living room floor.

Internal leak detection of this kind — working systematically through pressure isolation, tracer gas, and acoustic correlation — is what allows a precise location to be established without unnecessary disruption to the property.

Investigation Process

1. 1
   Symptom noted on arrival

   The customer showed the engineer a damp patch on the ceiling and wall in the living room, which was the starting point for the investigation.

2. 2
   Stop tap isolated and system drained

   The internal stop tap in the kitchen corner unit was closed and the system was fully drained down before testing began.

3. 3
   Pressure test carried out

   Testing equipment was connected to the cold mains and the pipework was pressurised to 1.5 bar. After 15 minutes, pressure had dropped by 0.1 bar, confirming a leak was present.

4. 4
   Heating system isolated and retested

   The heating circuit was isolated and the pressure test repeated. Pressure continued to fall, ruling out the heating system as the source.

5. 5
   Hot water system isolated and retested

   The hot water system was then isolated. Pressure still continued to drop, confirming the fault was on the cold feed.

6. 6
   Tracer gas introduced

   Tracer gas was introduced into the system in an attempt to locate the leak, but the leak rate was too high for the method to produce a usable result.

7. 7
   Acoustic testing carried out

   Acoustic equipment was deployed and produced a positive signal, identifying the area of the living room floor where the leak was located.

8. 8
   Carpet lifted and floorboards removed

   The carpet was lifted over the identified area, revealing a damp patch on the floorboards. The boards were removed to expose the pipework beneath.

9. 9
   Pinhole leak found and repaired

   A pinhole leak was identified on the cold feed pipe. Approximately eight inches of damaged copper pipe were cut out and replaced using two press-fit couplings and new copper pipe.

10. 10
    Floor reinstated

    The floorboards were refitted and the carpet was relaid, leaving the floor in the same condition as before work began.

Result & Outcome

The leak was found beneath the living room floor on the cold feed pipe. A pinhole had developed in the copper, allowing water to track upward and appear as dampness on the ceiling and wall above. Acoustic testing was the method that delivered the result after tracer gas was ruled out due to the leak rate — a common situation in internal leak detection where the appropriate method depends on conditions found on the day.

The repair involved cutting out approximately eight inches of the damaged copper pipe and fitting a new section using two press-fit couplings. This is a clean, reliable repair method that avoids the need for soldering in a confined underfloor space. Once the pipe was replaced, the floorboards and carpet were refitted.

With the cold feed restored and the floor reinstated, the source of the damp has been eliminated. No further recommendations were made, indicating the remainder of the system was found to be in satisfactory condition.