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Case study: Sydney Water trunk main correlation

Supplier: Gutermann
20 July, 2011

The equipment used was the Gutermann Aquascan TM Correlator to locate the leak position and the Aquascope 3 Leak detector to pinpoint the leak position.

From the Map above 2 locations are shown, these were where the Hydrophone Sensors were fitted to the Hydrants. Location 1, junction of Lillyfield road and Victoria Road was on the 600mm TM where as Location 2 Robert St, was on a new Hydrant on a 300mm off take.

The photo above is a view from the footbridge over Victoria Rd, adjacent to location 1 looking towards Roberts Road. The 600mm TM runs along the middle of the left hand west bound lane before crossing towards Roberts Rd.

A water tight connection is important as any leakage close to the Hydrophone would be picked up during the correlation process.

The Results

The first correlation was over 265m made up of 240m of 600mm CI, 14m of 500mm CI and a 200mm CI off take of 14m. Initially it was discover there was a large noise created at sensor A which was probably due to the loop at that point. Peak suppression and filtering was used to remove this large noise.

There was a couple of peaks of interest, one at 77.6m from Sensor B and another around 30 to 35m from Sensor A. The measurements were taken from the Hydra system so there maybe some errors in this which will effect the true leak distances the correlator calculates. On closer inspection of the point closer to sensor A, a service connection was discovered which used to feed the old White Bay Hotel which has since been demolished. This connection was open and leaking therefore the Sydney Water crew capped off the disused service. A noise could still be heard on the capped, disused service so a correlation was made from Sensor A, Lillyfield Rd to the capped exposed service. The result is shown above.

The Aquascan TM correlator gave a result of 26.9m from B which was correct and this was confirmed with an Aquascope 3 ground Mic. A loud clear leak sound could be heard from the main tap feral connection. As the service was disused the plan was to cap the main tap to prevent future issues. The repair was planned for the Sunday after the correlation exercise as this would cause minimum disruption to the busy Victoria road traffic.