This one piece inlet control incorporates several different control devices in one. It is specifically designed for use on an unvented system to control the incoming water supply to a hot water cylinder. It includes: a ‘droptight’ pressure reducing valve, meaning the valve will hold at the pre-set pressure regardless of whether under flow or no flow conditions and regardless of fluctuating inlet pressures. It also incorporates a single check valve which will protect the system against backflow prevention up to fluid category 2, and a pre-set expansion relief valve which will prevent over pressurisation. The expansion relief valve is designed so it can rotate, to allow the discharge connection to be fitted in various directions making installation easier.