A liquid heater comprising a plurality of storage compartments for containing liquid to be heated. The storage compartments being connected together in series and comprising at least a first end compartment for receiving liquid to be heated and a second end compartment from which heated liquid can be drawn. A heating means is provided in each compartment for heating the liquid contained therein. A first flow control means is operable to allow liquid in one compartment to flow into the next compartment in a flow direction towards the first end compartment when liquid contained in said one compartment reaches a predetermined temperature. A second flow control means is operable to allow liquid flow from one compartment to the next compartment in a flow direction towards the second end compartment while preventing reverse flow.