This European Standard specifies dimensions, materials and performance requirements (including methods of test) for hydraulic safety groups, of nominal sizes from DN 15 to DN 40, having working pressures from 0,1 MPa (1 bar) to 0,7 MPa (7 bar). Hydraulic safety groups are intended for fitting to the cold water supply of storage water heaters, having a maximum distribution temperature of 95°C, for all energy sources. Hydraulic safety groups control and limit the pressure in hot water heaters and prevent, by one function, the backflow of warm water into the circuit, and the contamination of water in the water heaters by the discharged water.