This document specifies the field of application, the dimensional, the physico-chemical, the design, the hydraulic, the mechanical, and the acoustic characteristics of controllable backflow preventers with reduced pressure zone, Family B, Type A. This document covers controllable backflow preventers of Family B, Type A, with reduced pressure zones, intended to prevent pollution of potable water by backflow, caused by backsiphonage or by backpressure. It is applicable to controllable backflow preventers in denominations DN 6 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 for maximum 1 h at 90 °C. It specifies also the test methods and requirements for verifying their characteristics, the marking and the presentation at delivery.