1293959 Water heaters FROLING GmbH & CO KG GEB 3 Dec 1969 59014/69 Heading F4A A multiple flow warm water heater 1 has service water in heat exchange tubes within a heat exchange region 2, the tubes being provided with an inlet 4 and outlet 5, heated by first and second heating liquids at different temperatures having inlets 16 and 12 for the second and first liquids respectively and a common outlet 15, and includes a space 8 communicating with the region 2 at different vertical levels. The tubes are connected by a manifold 3 which has an inlet 6 and check valve 7 for return service water. The inlet 12 for the first heating water, generally the return flow from a central heating system, leads to a turbulence reducing compartment 13 surmounted by a baffle 14. The inlet 16 for the second heating water, which may be the preflow of the central heating system, is provided with a valve 18 controlled by a temperature probe 19 in the service water outlet 5. A baffle 17 directs the hot heating water to the heat exchange region 2. In use, any difference in temperature between water entering through inlet 12 and water in the heat exchange region may set up convection currents so that water will pass from the space 8 to the heat exchange region through outlet 11 or at the top. If the service water is not heated sufficiently the valve 18 opens to allow hot water into the heat exchange region 2. In other embodiments, Figs. 2-4 (not shown), the space may surround the heat exchange region or be located between inner and outer heat exchange regions, or the space may be divided into two chambers by the heat exchange region.