Underground Water Mains Leak Detection in Addlestone

Symptoms

A large park home site in KT16, with up to 150 individual buildings, was experiencing a failure of water supply across a significant portion of the site. The site operates a split supply arrangement: roughly a third of the park home units are fed directly from the mains, while the remaining two thirds are served by a rising main that fills a water tower, with gravity feed to three booster pumps distributing water across the rest of the site.

The booster pumps were running continuously but unable to achieve any sustained head of pressure, and there were signs of air passing through the pump system — indicating the tower was not holding sufficient water volume.

Methods Used

Given the scale and complexity of the site, the investigation began with a systematic assessment of the entire supply hierarchy rather than targeting individual units. An initial meter test at the incoming supply recorded water usage of approximately 3 cubic metres per hour — a figure that represented the combined draw of normal site consumption, the continuous attempt to refill the water tower, and any active leaks.

Pressure testing confirmed the incoming mains pressure was approximately 2.5 bar, with a notably low flow rate. Sectional isolation of the pumped distribution system confirmed a significant leak was present downstream of the pumps.

The pump outlets were closed for approximately 20 minutes to allow water to accumulate in the tower; on retesting, a moderate pressure was achieved briefly, confirming the infrastructure itself was functional and narrowing the investigation to leak location.

Investigation Process

1. 1
   Initial site inspection and meter test

   On arrival, the plumbing infrastructure across the site was reviewed and an initial meter test recorded approximately 3 cubic metres per hour of water usage — reflecting combined site consumption, continuous tower refilling, and active leaks.

2. 2
   Mains pressure assessment

   Pressure testing at the incoming supply confirmed approximately 2.5 bar mains pressure with a low flow rate, ruling out critically low incoming pressure as the sole cause of the system failure.

3. 3
   Pump system observation

   Two of the three booster pumps were found running continuously but unable to achieve pressure, with air passing through the pump heads — consistent with the water tower being unable to maintain adequate water volume.

4. 4
   Sectional isolation of pumped supply

   Isolation testing of the pump supply confirmed a significant leak was present within the pumped distribution network. Pump outlets were closed for approximately 20 minutes to allow the tower to accumulate water, after which the pumps achieved moderate pressure briefly on retesting.

5. 5
   Expansion vessel pipework leak identified

   During the pump room inspection, a leak on the copper pipework connecting to the system expansion vessel was noted, with visible signs of severe erosion to that pipework.

6. 6
   Acoustic tracing through drainage network

   Acoustic testing across the site detected strong water flow noise within the drain system. The drains were followed along three roads until the final entry point to the drainage system was identified in front of a disused site.

7. 7
   Leak pinpointed on disused plot

   Further focused acoustic testing on the disused plot located the leak to a specific point in the middle of the area. The pipework was exposed at that location and the leak confirmed and repaired.

8. 8
   System retested and expansion vessel repair made

   Following the ground repair, the system was retested and good flow and pressure were achieved. Under restored pressure, the expansion vessel pipework leak increased significantly and a temporary repair was made to prevent further loss.

Result & Outcome

The active leak was located on failed pipework within a disused site on the park home estate, identified through acoustic correlation after tracing water flow through the site's drain network along three roads. Once exposed and repaired, the system was retested and both flow and pressure were restored across the pumped supply network. The combined leak rate from the failed underground pipework and the expansion vessel connection was estimated at between 200 and 500 litres per hour — a rate sufficient on this size of site to continuously overwhelm the storage tower's capacity, particularly in the context of the recent off-site supply disruption.