This document specifies:a)field of application;b)requirements for hose union backflow preventer;c)dimensional and the physico-chemical properties and the properties of general hydraulic, mechanical and acoustic design of hose union backflow preventers DN 15 to DN 32;d)test method and requirements for verifying these properties;e)marking and presentation;f)acoustics.This document specifies the characteristics of hose union backflow preventers DN 15 to DN 32 that are suit-able for use in drinking water systems at pressures up to 1 MPa (10 bar) and temperatures up to 65 °C and for 1 h at 90 °C.