Used on the pump outlet of a water supply system to prevent medium's back-flow.water hammer and water shock.combining three functions as an elec-tric valve,check valve and water hammer remove r,capable of effectively raisingsafety and reliability of the water supply system,integrating the technical principle of slow-open,speed valve,slow-close removing water hammer and preventing both pump-starting and pump-stopping water hammers from being formed The gate can automatically carry out open-close upon the operation rules of the water pump just by operating the pump t0 open or close electrically This valve features a big flow and a small pressure loss.reliable sealing performance,easy installation,debugging and maintenance and a long duration.