National Grid Gas was fined by Dudley Magistrates' Court after causing a gas leak into a Halesowen home.
Engineers were replacing the gas supply to a property in Bromsgrove Road, Hunnington, when they inadvertently drilled through a plastic main contained within the iron main which they did not know was there. Gas leaked out and found its way into another house approximately 150 metres away from the first.
Later that afternoon a member of the public reported a smell of gas and a second team of engineers came out to investigate. The leak was located and the escaping gas was finally made safe in the early hours of the following morning.
The Health and Safety executive (HSE) said the leak would not have occured had National Grid Gas updated its records to show the existence of the plastic main, which they had known about for four years.
The company pleaded guilty to breaching the Health and Safety at Work etc Act 1974 and was fined £17,500 with £8,192 costs.
It's common for plastic mains to be inserted into an existing iron main, when iron mains are replaced. The gas is then contained within the plastic main.
HSE inspector Francine Cheney said: "The company had procedures in place to allow for records to be corrected, but then failed to follow them.
"The risk to members of the public was extremely high, which underlines the importance of operators having accurate pipeline records. The hole that had been drilled was three quarters of an inch wide, and allowed more than half a tonne of gas to escape - enough to result in an explosion had it been ignited. It was extremely fortunate the owners were away at the time."