Type BV piston valves as a rule open into the valve and therefore keep the entire cross section of the housing open. Furthermore, it is possible to use the piston to break through a crust and then open into the valve.

If the container is covered with soil it is difficult to install a valve under the container. Therefore, for Type BVS valves, the valve had to be placed into the tank. Weights make sure that the valve is closed securely in case the controlling air pressure should fail.