The “nozzle” check valves should be used in order to grant a good performance of the anti-hammer effect. These valves are nozzle type, they ensure a rapid, shock free closing before any change in the flow direction, and a noiseless operation, as well as low water losses thanks to their design. For this reason, “nozzle” non return valves are suitable for both vertical, horizontal and oblique installation in those critical and severe pumps and compressor applications.