A short while ago I decided to put a through the wall air con in my workshop. No problem, cut and knocked out the bricks on the outside wall, perfect. Looking through the hole I was surprised to see a copper pipe running vertically through the middle of the hole. No problem I think to myself, it's only the water pipe, so I pop down to bunnings and get all the gear to do a work around, still no problem. I go and turn the water off at the mains and take a hacksaw to the offending piece of pipe.
This is when the hissing sound started. Problem. I'd cut the gas line into the house. The guy from the emergency gas repair service wasn't very understanding and just kept shaking his head and mumbling something about my lack of intelligence and parentage.