Hot Water System Leak Detection in Knaphill

Symptoms

The lobby wall and the adjoining utility kitchen wall both showed heavy damp, reinforcing that water had been migrating through the structure. A job requiring hot water leak detection of this kind — where pressure loss is absent but thermal and moisture indicators are present — calls for a multi-method approach to pinpoint the source without unnecessary excavation.

Methods Used

This multi-tool approach is standard practice in hot water leak detection where the pipe runs beneath a solid floor. Each method independently pointed to the same area, giving high confidence before excavation began.

Investigation Process

1. 1
   Initial observations on arrival

   The engineer noted bubbling paintwork on the lobby wall, a warm floor, and heavy damp on both the lobby and utility kitchen walls. The heating system showed no pressure loss.

2. 2
   Thermal imaging survey

   Thermal imaging was carried out across the lobby floor. The camera identified the pipe route and located a distinct hot spot consistent with a subsurface hot water leak.

3. 3
   Damp meter readings

   High damp readings were recorded in the same area as the thermal anomaly, confirming moisture migration through the floor and wall structures.

4. 4
   Pressure testing — cold feed

   A pressure test was applied to the cold feed pipework. The test passed, indicating no leaks on that circuit.

5. 5
   Pressure testing — hot feed

   A pressure test was applied to the hot feed pipework. This test failed, confirming a leak on the hot water side.

6. 6
   Acoustic survey

   Acoustic equipment was deployed and detected an anomaly at the same location already identified by thermal imaging and damp readings.

7. 7
   Floor exposed and first leak found

   The lobby vinyl and concrete floor were opened up. A hairline crack was found on a 15mm copper pipe. The damaged section was replaced, but a retest failed — indicating a second leak remained.

8. 8
   Second leak located and repaired

   A second leak was found approximately 15cm from the first. Both sections were replaced with copper pipe and fittings with lagging.

9. 9
   Final pressure retest

   On completion of both repairs, the pipework was pressure tested at 4 bar for 20 minutes. The test passed, indicating no further leaks at the time of testing.

Result & Outcome

The engineer noted that the ground floor pipework is in poor condition and recommended full replacement. This is consistent with two cracks being found in close proximity — the repaired sections are sound, but the wider pipework remains a risk.