Water Mains Leak Detection in Coventry

Symptoms

At a property in CV5, water was pooling in the cupboard beneath the staircase, and both the hallway and bathroom floors were uniformly damp. The source was not immediately obvious — the symptoms could have pointed to a supply pipe leak, a leaking WC cistern, or a failing heating system.

The combination boiler was losing pressure over a two-week period, which raised the possibility of a central heating leak. However, given the volume of water present on the floors, it was assessed as unlikely that such a slow pressure loss was responsible.

The engineer advised the customer that a pressure loss of at least 1.5 bar over 24 hours would be required before the heating system could be meaningfully investigated as the source.

This job required full internal leak detection to isolate and identify the source or sources of the leak before any repair could be planned.

Methods Used

The investigation began by establishing which system was losing water. The water meter was monitored with the internal stop valve open and then closed, confirming the leak was on the internal supply pipework rather than the external mains.

The hot water and heating circuits were then separated from the cold mains for individual pressure testing.

Pressure testing at 4 bar for 30 minutes was applied to the external mains, internal mains, and hot supply pipework in sequence. A leak from the ball valve in the WC cistern was identified first; once the servicing valve to the WC was closed, a separate fault was confirmed on the hot supply pipework.

Tracer gas was introduced at the kitchen sink, and a gas trace was detected almost immediately in the hallway outside the bathroom door. Thermal imaging was then used to track the pipework route and pinpoint the precise location for excavation.

This methodical approach is what internal leak detection requires when multiple potential sources are present.

Investigation Process

1. 1
   Water meter monitored

   The water meter was checked with the internal stop valve open and then closed. Continuous usage of 6 litres per hour dropped to zero when the valve was closed, confirming the leak was on the internal supply pipework.

2. 2
   Heating system assessed

   The combination boiler was noted to be losing pressure over two weeks. Given the volume of water on the floors, this was assessed as insufficient to be the primary cause, and the customer was advised of the threshold required to investigate the heating circuit further.

3. 3
   Individual pressure tests carried out

   The external mains, internal mains, and hot supply pipework were each pressure tested at 4 bar for 30 minutes to isolate the faulty circuit.

4. 4
   WC cistern ball valve fault identified

   A leak from the ball valve in the WC cistern was located during testing. The servicing valve to the WC was closed to isolate this fault and allow continued testing of the remaining circuits.

5. 5
   Fault confirmed on hot supply pipework

   With the WC isolated, pressure testing confirmed a separate leak on the hot supply pipework.

6. 6
   Tracer gas introduced

   Tracer gas was introduced into the hot supply pipework at the kitchen sink. A gas trace was detected almost immediately in the hallway outside the bathroom door.

7. 7
   Thermal imaging used to track pipework

   The pipework route was tracked using thermal imaging, confirming the location in the hallway and guiding the excavation.

8. 8
   Area excavated, leak exposed

   The area was excavated, exposing the leaking copper tube. The damage appeared to have been caused by physical impact during the original installation.

9. 9
   Leaking section cut out and renewed

   The damaged section of pipe was removed and replaced using two 15mm couplings, one 15mm elbow, and 2 metres of 15mm copper tube.

10. 10
    Post-repair pressure test passed

    A pressure test at 4 bar for 30 minutes was carried out on the repaired pipework with no pressure loss, confirming a sound repair.

11. 11
    Supply reinstated and pipework flushed

    The water supply was reinstated and the pipework was thoroughly flushed. The customer was advised to replace the ball valve in the WC cistern.

Result & Outcome

The leak was located in the hallway outside the bathroom door, where the hot supply pipework had been physically damaged during the original installation. The combination of tracer gas detection and thermal imaging pinpointed the location precisely enough to excavate directly to the pipe without unnecessary disruption.

The damaged section was cut out and replaced. A post-repair pressure test at 4 bar for 30 minutes confirmed no further loss of pressure. The supply was reinstated and the pipework flushed before the job was completed.

For this internal leak detection case, two separate faults were identified: the repaired pipe leak and an outstanding ball valve fault in the WC cistern. The customer has been advised to replace the WC cistern ball valve as a separate follow-up item. Once that is addressed, both sources of water loss at the property will have been resolved.