Buffer tank

A buffer tank is a vessel of heating-system water fitted into a heat pump or heating circuit to add volume, steady flow conditions or a hydraulic break between the heat pump side and the emitter circuits. In heat pump paperwork it may be used to meet a minimum water-volume requirement, support stable flow, help defrost operation or act as a low-loss-header-style separator, depending on how it is connected. It is not the domestic hot water cylinder, expansion vessel, heat pump itself, heat-loss calculation, MCS certificate, commissioning record, warranty approval, planning permission or promise that the system will run efficiently.