After putting in a few more ties it was time to mark where the septic tank inflow pipe to the house was. The septic guy came over with a metal detector and declared it discovered. I decided it was a good idea to dig and check. Instead of going out the west side of the tank the pipe went out the north side, took and approximate 90 degree turn, and headed west toward the house. This had it pass under the deck about 6 feet away from where it originally was marked. The purpose it to avoid breaking the septic pipe when putting in footings. It was good that I dug and checked.