V Type: Vacuum Valve operates when the vacuum is created in the system or the main pipe , the air valve open quickly to break the vacuum by taking in air. The inlet of Air valve is sealed under the water pressure. 
K type: Kinetic valves evacuates air quickly during the water filling of the pipeline and also withdraws massive air while water is draining. With the aerodynamic design, the valve can avoid too much air accumulation or negative vacuum formation, and the valve inlet has a tight sealing in the process of low pressure operation. 
C type: Combined valves combine the Massive air release during water filling of the pipeline and the efficient exhaust of little air under pressurized operation and the air intake in Vacuum situations. The aerodynamic design of the valve avoid too much air accumulation or negative vacuum formation, and the valve inlet also has a tight sealing in the process of low pressure operation.