Finding buried septic tanks can pose issues, especially if there are no records nor any obvious clean-outs to use for locating purposes. Here are some suggestions of ways to locate tanks that are buried.
Start at the county/local regulator. Some county records have as-builts that were drawn during system installation. I’ve seen some as-builts that triangulate the location using dimensions from two different locations. Triangulation gives very accurate locations for where to dig. Some county inspectors are now using GPS/GNSS to locate tanks and distribution cells with 100% accuracy. But there will always be those old tanks with no records at
