Gutermann International

The residential area of Dalneigh in Inverness was causing confusion within Scottish Water’s Northern Operations. The area had indicated an increase in minimum night flow and so a number of radio acoustic loggers were deployed in the area to try to locate the leak. After downloading 7 of these radio loggers indicated the presence of a leak. These loggers were all located around a single area of interest.

The local leakage engineer surveyed this area of interest with a leading leak noise correlator but found no conclusive leak indication. This correlator was used later the same day to locate a leak in another area.

A ZONESCAN 800 survey was commissioned in this area to try and confirm or deny the presence of any leakage.

It can clearly be seen from the above map, and the Project Table opposite, that only
2 loggers have indicated the potential presence of leak noise. The other radio loggers used previously had indicated leakage in the whole area surrounding the location of logger 100084.

These other radio logger also failed to indicate the obvious leak noise at the location of logger 100069. Which is the supply pipe to the high school.

The leak noise indicated on both loggers is low on the decibel scale but very obviously leak noise. Correlations were carried out between logger 100084 and it’s adjacent loggers with all the results being inconclusive. Further investigation revealed that the hydrant on which 100084 was located had a leaking frost plug.

Correlations were also carried out between logger 100069 and it’s adjacent loggers, again the results were all inconclusive. It is suspected that there is overnight usage in the high school due to poor maintenance or lack of water conservation devices.

These results indicated that the increase in metered minimum night flow was not attributable to this particular area of Dalneigh and that further investigation was required.

Summary:

The ZONESCAN 800 survey took just 20 minutes. A correlation survey was completed 10 minutes later using sound signals recorded by the ZONESCAN 800 loggers, and an accurate worksheet was subsequently submitted. This was in comparison to wasting 4 hours plus chasing “leaks” that quite simply did not exist.