Water Mains Leak Detection in Baildon

Symptoms

A property in LS29 had received a notice indicating a leak was present. On arrival, the customer explained the situation and also mentioned a hissing noise coming from one of the classrooms — a detail that would prove significant during the investigation.

Before any internal work began, the external water mains meter was checked and timed. It was passing one litre every five seconds, confirming active water loss.

A visible sign of escape was also found outside: an area of the field closest to the classroom with the hissing noise was saturated with water.

This combination — a running meter, waterlogged ground, and an audible hissing — pointed clearly to a pressurised leak on the pipework serving that part of the building. Internal leak detection was required to pinpoint the exact location before any remedial decision could be made.

Methods Used

The investigation began at the external meter to quantify water loss, then moved to a site-wide inspection to identify visible signs of escape. Once the saturated ground near the affected classroom was noted, the stopcock supplying that section of the building was isolated.

The hissing noise stopped and meter movement reduced significantly, confirming the leak was on that branch of pipework.

With the affected supply confirmed, tracer gas was introduced to the pipework serving that side of the building. The property was then walked and inspected with detection equipment.

Gas was detected inside the classroom that had been making the hissing noise, and acoustic equipment was used to narrow the location down to the buried pipework feeding the teacher's desk tap. This structured approach — typical of thorough internal leak detection — allowed the leak to be located precisely without unnecessary opening up of the fabric of the building.

Investigation Process

1. 1
   External Meter Timed

   The external water mains meter was inspected and timed. It was passing one litre every five seconds, confirming active and significant water loss.

2. 2
   Saturated Ground Identified

   A site inspection found the area of the field closest to the classroom with the hissing noise was heavily saturated, indicating water escaping in that vicinity.

3. 3
   Affected Supply Isolated

   The stopcock supplying water to that section of the building was closed. The hissing noise stopped and meter movement reduced to a minimal level, confirming the leak was on that branch.

4. 4
   Tracer Gas Test Conducted

   Tracer gas was introduced to the pipework supplying the affected side of the building. Inspection of the property revealed gas escaping inside the classroom that had been making the hissing noise.

5. 5
   Acoustic Equipment Used

   Acoustic detection was carried out on the pipework in the classroom. Water movement was identified on the buried pipe supplying the teacher's desk tap, pinpointing the leak location.

6. 6
   Repair Options Discussed with Customer

   The engineer explained the two options: excavate the buried pipework to carry out a full repair (requiring removal of cupboards), or cap off the supply to the teacher's desk tap as a cost-effective alternative. The customer agreed to cap off the supply.

7. 7
   Supply Capped Off

   A 15mm compression fitting stop end cap was fitted to the pipework, isolating the teacher's desk tap supply and eliminating the source of the leak.

8. 8
   Pressure Test Completed

   A pressure test was carried out at 3.0 bar for 30 minutes using tracer gas. Pressure held at 3.0 bar throughout with no drop, confirming no remaining leaks on the supply for that part of the building.

Result & Outcome

The leak was located on the buried pipework feeding the teacher's desk tap in the classroom that had been producing the hissing noise. Tracer gas confirmed the leak was on that branch, and acoustic equipment identified the specific pipe run beneath the concrete floor as the source of water movement.

Given that the leaking pipe only supplied the teacher's desk tap, the customer was given a clear choice: excavate and repair, or cap off the supply. Capping was the more straightforward and cost-effective route, and the customer agreed. A 15mm compression fitting stop end cap was fitted to isolate that supply. A subsequent 30-minute pressure test at 3.0 bar showed no drop in pressure, confirming the remainder of the pipework on that side of the building is sound.

For a job involving internal leak detection in a school environment, this outcome avoided any unnecessary disruption to the building fabric. The only follow-up required is to inform the teacher in that classroom that the desk tap is no longer in service.