Where you have identified the need for an RPZ valve or your Water Company has instructed you to install one

An RPZ valve must be installed horizontally above the floor, with the relief valve discharging downwards. An in-line strainer should be included upstream of the valve to prevent fouling of the assembly elements. The valve should be in a location that enables effective inspection, testing and maintenance and must not be installed in concealed locations or locations liable to flooding, freezing, above electrical equipment or liable to mechanical or other damage.