Waste disposal is one of the most important problems that the owners of suburban cottages, cottages and private houses regularly face. A common solution is the arrangement of a cesspool. But it needs to be constantly emptying, which entails additional difficulties. A good replacement can be a septic tank or a bioseptic AK4-7. This is a universal and functional treatment structure. However, a wide variety of types and modifications of septic tanks make their choice and acquisition quite difficult.