We are trying to locate the septic tank on a house we have a contract on. The septic company couldn't find it and said they will need to bring out a backhoe. We went out and tried again to find it. One of the difficulties is that the land behind the house is on a rock shelf. Everywhere we poke there is rock. The neighbor told us that when the former owner put in a cistern, they had to dig through rock, so it is still possible the septic is close to the house and they dug through the rock. I have read that maybe we could find the septic lid with a metal detector. Has anyone tried this? I appreciate any help!!