Underground Water Mains Leak Detection in Chatteris

Symptoms

To confirm the source, both stopcocks were checked — the main residence stopcock and the separate garage stopcock. With both closed, the external water meter continued to show movement, isolating the leak to the section of pipework between the meter and the stopcocks.

This is a reliable indicator in water mains leak detection: if the meter runs with all internal isolation confirmed, the loss is external and underground.

Methods Used

Gas was detected bubbling up through the soil at the front of the property, giving a precise location before any excavation began. Pressure testing supported the isolation confirmation already established through the stopcock checks.

Visual inspection was carried out once the excavation exposed the pipework.

Investigation Process

1. 1
   Stopcocks isolated and meter checked

   Both the main residence stopcock and the garage stopcock were turned off. The external water meter continued to show movement, confirming the leak was on the external mains between the meter and the stopcocks.

2. 2
   Mains isolated at meter, tracer gas introduced

   The mains supply was turned off at the meter. Tracer gas was connected into the cold main pipework via the garage, with the pipe pressurised with gas to locate the escape point.

3. 3
   Gas detected at the front of the property

   Tracer gas was quickly detected bubbling out of the soil at the front of the property, identifying a precise location for excavation.

4. 4
   Excavation carried out

   With the customer's assistance, a large hole was dug at the indicated location, exposing the buried pipework at the leak point.

5. 5
   Defective fitting identified

   A brass 22mm compression tee wrapped in Denso tape was found. One compression nut was loose and the olive was split — the fitting was not appropriate for use on mains pipework.

6. 6
   Correct fitting sourced and installed

   An appropriate replacement fitting was purchased from the merchants. The tee was replaced, and the garage pipework was reconnected.

7. 7
   System tested and confirmed clear

   The system was tested after the repair, with no further movement detected on the external water meter.

Result & Outcome

The customer has been advised that other inappropriate fittings may remain elsewhere on the pipework, given the nature of what was found. The customer is considering having the supply replaced with new MDPE pipe in the future, which would remove the risk posed by any remaining unsuitable fittings on the existing mains.