The difference between backflow preventer and check valve
The backflow preventer consists of two separated check valves and a drain valve. Due to the local head loss of the check valve, the pressure in the middle cavity is always lower than the pressure at the inlet. This pressure difference causes the drain valve to be closed and the pipe is in normal water supply.
Plain and simpleBackflow preventer is double acting, better than check valve
In abnormal pressure (i.e., the outlet pressure is higher than that of the middle cavity), even if the two check valve can not reverse sealing, safety relief valve can automatically open the reverse water emptying, and the formation of air separation, ensure the health and safety of water upstream.
