When a septic tank requires anti-floatation measures, several approaches can be employed.
One of them is the use of concrete. When concrete is submerged, it weighs about 85 pounds per cubic foot. If concrete is submerged for anti-floatation, then 85 pounds per cubic foot is used to calculate how much is needed. Some designers will specify the use of a concrete collar over or around the tank. The design should specify compaction requirements for backfill below the collar and details on the volume of concrete to be placed around the tank.
Another important consideration is how the concrete is attached to the
