I have very limited knowledge on pipe lasers in general. All my experience with them is new sewer installs where everything is staked out and grades are on the blue prints. The challenge I am faced with now is I need to rehab an active sewer, the inspector really wants me to use a pipe laser but I do not know how to sit one up in an existing active sewer line. There is no grades to follow on paper other then "match existing grade" however no one knows what current grade is. I have to be dead on as we are tying into exiting manholes, any advice is greatly appreciated.