I've used Hoffman Texas, Inc. DBA Roto-Rooter Service out of Irving a couple of times. They were quick and did a good job. They can do a video of your sewer pipe to see where the leak is. I had standing water in the back yard, because the renter took out the clean out plug and let gray water drain in the back yard, until I discovered what he was up to. Their number is 972-986-1978