Underground Water Mains Leak Detection in Maidstone

Symptoms

A property in ME17 had a reported water mains leak running at approximately 250 litres per hour. The supply system serving the property was a mixed-material mains run: a recently relaid section of blue MDPE pipe crossing a field, connecting at one end into black Alkathene pipe and at the other end onto existing steel pipe feeding the farmhouse and troughs.

The scale of the loss and the length of pipework involved made pinpointing the source far from straightforward.

Methods Used

The investigation began by isolating and pressure testing the newly laid blue MDPE section from the meter connection. With that section confirmed sound, attention shifted to the upper half of the system — from the blue MDPE up to the farmhouse and troughs — which failed its pressure test, indicating the leak was located somewhere in that stretch of pipework.

This is a standard approach in water mains leak detection: systematically eliminating sections to narrow the search zone before deploying more targeted equipment. Once the area around the farmhouse was identified as suspect, tracer gas was introduced at a garden tap near the office, and the yard, barn, and house perimeter were walked with a gas analyser to track escaping gas.

Ground microphones then confirmed the precise location by acoustic signal, with the strongest readings coinciding exactly with the highest gas concentration detected outside the kitchen window near the soil stack.

Investigation Process

1. 1
   MDPE section isolated and meter observed

   The connection between the new blue MDPE pipe and the existing steel pipe was disconnected and capped. No water usage was recorded at the meter, and a 15-minute pressure test confirmed the section from the meter to that connection was sound.

2. 2
   Upper system pressure tested — leak zone identified

   The upper half of the pipework, from the blue MDPE through to the farmhouse and troughs, was pressure tested and found to slowly lose pressure, confirming the leak was located somewhere in this stretch.

3. 3
   Tracer gas introduced near the house

   Pressure test equipment was repositioned to a garden tap next to the office. Tracer gas was added to the pipework in this area and the yard, barn, and house perimeter were walked with a gas analyser.

4. 4
   Leak area identified outside kitchen window

   Escaping tracer gas was detected in the ground outside the kitchen window close to the soil stack. Ground microphones confirmed the location, with the strongest acoustic signal matching exactly where the highest gas concentration was recorded.

5. 5
   Excavation and first repair carried out

   Customer consent was given and the ground was excavated to expose the pipework. A corroded section of steel pipe was cut out and replaced using transition couplings and blue MDPE pipe.

6. 6
   Second leak discovered during repair testing

   While testing the first repair, a second leak became evident a couple of inches from the original cut. Both repairs were removed and the steel pipe was cut further back towards the property to eliminate as much of the corroded section as possible.

7. 7
   Final repair completed and verified

   With the repair completed for the second time, a low-pressure test showed no loss of pressure. A 15-minute meter observation recorded zero water usage, confirming all pipework from the meter to the house and troughs was sound at the time of testing.

Result & Outcome

Two lateral fractures were found on a severely corroded section of thin-wall steel pipe located outside the kitchen window, close to the soil stack. The first fracture was cut out and repaired, but a second fracture emerged just inches away during testing. Both sections were removed and the steel pipe was cut back as far toward the property as conditions allowed, with transition couplings and blue MDPE pipe used to complete the repair. A 15-minute meter observation following the repair recorded no water usage, confirming the system was sound at the time of completion.

The steel pipe exposed during excavation was in very poor condition. The thin-wall section — which connects through the wall into the property — showed the most significant corrosion, and both fractures found were lateral breaks consistent with advanced pipe deterioration. Given this, a further failure on the remaining steel pipe entering the property must be considered a near certainty without further action.

For a water mains leak detection job of this nature — mixed-material pipework across a large rural site — the systematic isolation approach, combined with tracer gas and acoustic confirmation, was essential in avoiding unnecessary excavation across the full mains run. The recommendation to replace the remaining thin-wall steel pipe from the repair point into the property stands as the most important follow-up action to prevent a repeat situation.