The water pipe jumper is an easy thing to identify as missing, the plumbers need to be even more careful where opening gas lines. We had an instance where a gas line was carrying 6 - 8 amps of neutral current. The gas technician shut off the up stream valve, and when he broke the connection, the arc ignited the residual natural gas. This burned the hair off both his arms, he was very lucky. we found the neutral connection at the weatherhead had failed & the gas pipe was acting as the house neutral. (The water dept had experimenting with PVC & this house had a pvc water pipe from the street to just outside the cellar.)There was no driven grounds as the service was 30 - 40 years old.
