NOVELTY - The reducing agent storage system (2) has a feed device (16) which is adapted to feeding reducing agent (10) from a reducing agent tank (6) to a return device (14) via supply device (20) situated in between for reducing agent by venturi pump (18) drawing reducing agent from the tank through a return flow (B) of reducing agent led via the return device to a tapping container (8). A warming device (30) enables heat to be transferred from liquid heat medium (36) to reducing agent in the tank, the tapping container and the venturi pump to prevent freezing of the reducing agent.    USE - Reducing agent storage system for vehicle e.g. heavy trucks.    ADVANTAGE - Prevents freezing of the reducing agent by utilizing waste heat from the vehicle's engine since heat can be transferred from the liquid heat medium to the reducing agent in the reducing agent tank, the tapping container and the venturi pump. Enables warming of the reducing agent in the venturi pump since the heating loop for the liquid heat medium is associated thermally with parts of at least one from among the tapping container, the return device and the supply device for reducing agent and since the heating loop for liquid heat medium is associated thermally with more than one side of the venturi pump. Enables adapting the reducing agent storage system according to the engine's configuration since the liquid heat medium is either warmed directly by the engine through itself being the engine's cooling water or is warmed indirectly by the engine through being warmed by the engine. Provides a simple construction and fitting and avoiding leakage at the tank penetrations since the tapping device, the return device and the supply device for reducing agent take the form of pipes or hoses. Avoids air ingress into the tapping device while at the same time there is no need for a control unit to control filling of the tapping device.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a reducing agent warming method.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic of a reducing agent storage system for vehicle.    Reducing agent storage system (2)    Reducing agent tank (6)    Tapping container (8)    Feeding reducing agent (10)    Return device (14)    Feed device (16)    Venturi pump (18)    Supply device (20)    Warming device (30)    Liquid heat medium (36)    Return flow (B)