In the process of extending a basement sump pump's output discharge line far away from the house, the contractor sawed off the existing above ground steel pipe and connected the new underground discharge pipe. In doing so they inadvertently pulled off or jostled off the connection from the sump pump to the external line and when the pump started, over the course of 3 hours until we caught it, it flooded the basement. The contractor claims that if the interior pipes had been secure this wouldn't have happened. Who's responsible? The pump was functioning correctly with no issues of any kind up to this point. They are threatening to walk off the job in an hour if this isn't resolved. Help!