I once hired a contractor, certified in gas lines, to run a black pipe gas line in my attic to a second fireplace I built. Once he left, I saw the flame was barely there, so I crawled up in the attic and saw he failed to thread one gas pipe at all. It was cross threaded at a 45 degree connection, with no coupling, and you could shove a pencil into the opening, leaking gas into my attic for about a month. I had to go up there and fix all of his work myself, and stopped his final payment and explained with all the pictures of his shoddy work, I begged him to take me to court. He never did.