We replaced a gas line for a customer. We used a subcontractor who bored the gas line under ground and hit her sewer line. (They assume no responsibility since it is underground, their invoice states all this) We did not find out about the sewer line until 4 months later. She had another plumbing company out for a stoppage and agreed to complete work at which time until they dug up the line and found that our subcontractor who ran the gas line was what hit her sewer line. She had the other company complete the work and is requesting us to pay for the work since it was our subcontractor who hit the line. Mind you our job was about $3k, the work this other company did and she is requesting us to pay is $7k. Our owner thinks we are fully responsible, which we are willing to pay if we need to. But is there anything we can do. Or if we do take responsibility is there a letter we can present at that time stating we are no longer liable for any damages further etc....