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This European Standard specifies the field of application, the dimensional, the physico-chemical, the design, the hydraulic, the mechanical, and the acoustic characteristics of controllable backflow preventer with reduced pressure zone Family B Type A. This standard covers controllable backflow preventers of Family B Type A, with reduced pressure zones, intended to prevent backflow by backsiphoning or backpressure of water into the potable water distribution system whenever the pressure of the latter is lower than the system located downstream. It is applicable to controllable backflow preventers in denominations DN 8 up to DN 250. It covers controllable backflow preventers of PN 10 that are capable of working without modification or adjustment: - at any pressure up to 1 MPa (10 bar); - with any pressure variation up to 1 MPa (10 bar); - in permanent duty at a limited temperature of 65 °C and 90 °C for 1 h maximum. It specifies also the test methods and requirements for verifying their characteristics, the marking and the presentation at delivery.