11 hence no heat transfer can take place if the water 20 surrounding the condensing coil 11 is cooler than the collector 22 condensing of the vapor will commence and efficient heat transfer will take place between the collector 22 and the water 20 typical differential temperatures are less than 5 u00b0 f from the above description it can be seen that the system provides its own thermostat as well as providing a 34 thermodiode 34 so that heat can only flow in the proper direction further the bladder accumulator prevents the release of freon to the atmosphere and protects the system an alternate configuration where the hot water storage tank cannot be placed above the collector utilizes a condenser located above the collector rather than within or attached to the storage tank the heat is transferred from this condenser to the storage tank by means of a circulating pump for forcing circulation of the storage tank water through the condenser this then provides many of the benefits of the above system even though the optimum location of the storage tank is precluded a good performance monitor of the system is provided since the pressure gauge within the pressure regulating devices 21 indicates the actual.