Underground Water Mains Leak Detection in Nottingham

Symptoms

A property in NG7 housing two work units — each fitted with a toilet and two basins — was recording anomalous water consumption. Despite the limited sanitary use the units would typically see, utility bills pointed to usage in the region of 2,000 litres per hour on the suspect mains supply.

A water mains leak detection visit was arranged to establish the cause.

Engineers arrived on site to assess the situation. Initial meter monitoring confirmed an uncontrolled flow of 1 litre per second — far beyond anything the connected facilities could account for.

Despite the scale of the loss, no visible signs of water damage had been found anywhere on site prior to or during the initial assessment.

Methods Used

The investigation began with live flow metering at the meter, which confirmed continuous, uncontrolled usage. Tracer gas was then purged into the pipework and a full site sweep carried out using specialist gas analysers.

High concentrations of tracer gas were detected emitting from around drain covers close to the meter, narrowing the search area considerably.

With a zone of interest identified, a combined technique was applied — introducing both mains pressure and tracer gas simultaneously — while acoustic profiling was used to pinpoint the precise leak location beneath the cobbled surface between the drain and the unit wall. This is a standard staged approach in water mains leak detection: non-invasive methods are used to build confidence in a target area before any ground is broken.

The acoustic data raised a clear area of concern, and excavation was agreed with the customer on that basis.

Investigation Process

1. 1
   Site attendance and meter monitoring

   Engineers attended the property in NG7 to investigate high water consumption on a mains supply serving two work units. Live metering at the meter immediately recorded an uncontrolled flow of 1 litre per second.

2. 2
   Tracer gas introduction and site sweep

   Tracer gas was purged into the pipework and a full sweep of the site was carried out using specialist gas analysers. High tracer gas levels were found emitting from around the drain covers close to the meter.

3. 3
   Combined tracer gas and acoustic profiling

   A technique combining mains supply and tracer gas was applied, with acoustic profiling used to interrogate the area of concern. This raised a clear target zone beneath the cobbled surface between the drain covers and the unit wall.

4. 4
   Excavation and pipe exposure

   With customer agreement, excavation was carried out over the identified area. The mains was exposed and found to run below a drain; the supply pipe had become distorted and flattened.

5. 5
   Leak point confirmed and pipe section removed

   Further excavation exposed the leak point, located more or less directly beneath the drain. The affected section of pipe was cut out — it was found to be brittle and had deteriorated significantly.

6. 6
   Repair and reinstatement

   The damaged section was replaced with new 25mm MDPE pipe using specialist transition couplers and inserts. Pressure testing confirmed the supply was sound following the repair.

Result & Outcome

The leak was located beneath the cobbled surface directly under a drain, close to the meter. The supply pipe had become distorted, flattened, and brittle — physical deterioration consistent with the sustained and significant water loss being recorded. Excavation, guided by the combined acoustic and tracer gas findings, exposed the leak point precisely, and the damaged section was replaced with 25mm MDPE pipe using specialist transition couplers and inserts.

Post-repair pressure testing confirmed the supply was sound. However, given the condition of the removed pipe — brittle and structurally compromised — no guarantee could be given against further failures elsewhere on the same run. The outcome for water mains leak detection of this type is not just the repair itself but an honest assessment of residual risk, and that assessment here points to a broader issue with the pipework condition.

The recommendation is that if a further leak develops, the prudent course is to repipe the supply in full rather than carry out another point repair. The section removed gave a clear indication that the pipework as a whole has deteriorated beyond the point where individual repairs offer reliable long-term protection.