Finding buried septic tanks can pose issues, especially if there are no records nor any obvious cleanouts 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
