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Product overview

DF41/HS41 backflow preventer (antifouling block valve) is composed of two separated check valves and a hydraulic transmission to the drain valve. The valve body of the first check valve is equipped with a filter screen. Due to the local head loss of the check valve, the pressure in the middle chamber is always lower than that at the inlet. This differential pressure drives the drain valve to be closed and the pipeline supplies water normally. In case of abnormal pressure (i.e. the pressure at the outlet end is higher than that in the middle chamber), even if the two check valves cannot be sealed reversely, the safety drain valve can be opened automatically to empty the backwater and form an air partition to ensure the hygiene and safety of upstream water supply.