Detecting water leaks in Council pipes can be a tricky business because often the evidence drains away.

Council employed a specialist detection service last summer, who used acoustic equipment to listen for leaks on the network.

Group Manager of Infrastructure and Open Spaces Neil McCann said some leaks were obvious because you could see water pooling on grass.

“But many of the leaks in our pipe network are not obvious, because the pipes are buried deep underground and the leaks drain straight down.”

A leak on Catherwood Drive recently was one such example. The leak was “heard” and the pavement marked for inspection – there was still no sign of water when the pavement was lifted, but water was detected when the contractor began digging.

Mr McCann said the leak turned out to be significant, at 40 litres per minute.

“This latest round of detection work was on the west side of Ashburton and in Methven, and a total of 103 leaks were identified on the Council networks.

“Our maintenance contractor has been working through them as time and money permit and there are just a few left to fix. When that happens, we will be saving the equivalent of three Olympic-sized swimming pools of water a day.”

Mr McCann said the pipes in Methven had been checked for leaks two years ago and leaks found back then had been fixed.

“We go back for another acoustic round because often the sound of a bigger leak drowns out the sound of other leaks.”

Council has also written to property owners where leaks on private property are suspected.

A leak map helps staff better see the scope of problem areas and help programme pipe renewal.

Mr McCann said not all leaky pipes needed to be replaced.

“Some of our older cast iron pipes are still in surprisingly good condition and they just need to be cleaned or relined. Old does not always mean bad.”