Baxi 940503/810 expansion vessel RP250/6, type

Expansion tank CIMM RP250/6 type 9 for Baxi boilers, catalogue article 294.116.009-2, manufacturer code 294.116.009, from the expansion vessels category. This is a part of the type that absorbs the volume change of water as it heats, keeping system pressure within limits. In a heating circuit, the expansion vessel works alongside the safety valve; the vessel takes up excess volume, and if pressure still rises too far, the safety valve releases it. When selecting an expansion vessel, key parameters are its volume and pre-charge pressure, the connection thread type and size, the membrane material, and whether it is suitable for potable water if used in a domestic hot water system. Typical failures include loss of pre-charge pressure or a ruptured membrane, which cause system pressure to swing and the safety valve to discharge repeatedly. Replacement requires checking the vessel’s pre-charge with the system depressurised and matching the connection and volume to the system’s requirements. No specific dimensions, pressure ratings, or compatibility with individual Baxi boiler models are given; the part is designated for Baxi boilers in the catalogue, so confirm fit by comparing the physical connection and the system’s expansion volume needs before installing.