A system for heating a storage container for an aqueous operating liquid in a motor vehicle having a combustion engine cooled by means of a liquid heat transfer medium, using the waste heat from the combustion engine, which is transferred to the heat transfer medium, said system comprising a first heat exchanger , which is provided in or on the storage container and can be heated by means of the heat transfer medium in a cooling circuit of the combustion engine, wherein the first heat exchanger is part of a storage container heating circuit , which comprises a heat transfer medium feed and a heat transfer medium return , wherein the storage container heating circuit is connected hydraulically in parallel or hydraulically in series with a second heating circuit for heating the passenger cell of the motor vehicle, the storage container heating circuit comprises a valve with a controllable volume flow, characterized in that the storage container heating circuit comprises means for measuring or calculating the volume flow of heat transfer medium in the storage container heating circuit and means for controlling the valve in accordance with a plurality of temperature signals from a plurality of temperature sensors (T1 to T5), which are selected from a group comprising: - a temperature sensor (T4) in the heat transfer medium feed of the storage container heating circuit , - a temperature sensor (T5) in the heat transfer medium return of the storage container heating circuit , - a temperature sensor (T2) in the storage container , - a temperature sensor (T1) in the cooling circuit of the combustion engine, - a temperature sensor (T3) in the passenger cell, and - a temperature sensor (T3) in the second heating circuit . a first heat exchanger , which is provided in or on the storage container and can be heated by means of the heat transfer medium in a cooling circuit of the combustion engine, wherein the first heat exchanger is part of a storage container heating circuit , which comprises a heat transfer medium feed and a heat transfer medium return , wherein the storage container heating circuit is connected hydraulically in parallel or hydraulically in series with a second heating circuit for heating the passenger cell of the motor vehicle, the storage container heating circuit comprises a valve with a controllable volume flow, characterized in that the storage container heating circuit comprises means for measuring or calculating the volume flow of heat transfer medium in the storage container heating circuit and means for controlling the valve in accordance with a plurality of temperature signals from a plurality of temperature sensors (T1 to T5), which are selected from a group comprising: - a temperature sensor (T4) in the heat transfer medium feed of the storage container heating circuit , - a temperature sensor (T5) in the heat transfer medium return of the storage container heating circuit , - a temperature sensor (T2) in the storage container , - a temperature sensor (T1) in the cooling circuit of the combustion engine, - a temperature sensor (T3) in the passenger cell, and - a temperature sensor (T3) in the second heating circuit . - a temperature sensor (T4) in the heat transfer medium feed of the storage container heating circuit , - a temperature sensor (T5) in the heat transfer medium return of the storage container heating circuit , - a temperature sensor (T2) in the storage container , - a temperature sensor (T1) in the cooling circuit of the combustion engine, - a temperature sensor (T3) in the passenger cell, and - a temperature sensor (T3) in the second heating circuit . <EOS>