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1. A hot water supply cut-off system for use with an electric water heater to preclude the flow of unsafe water to a hot water distribution conduit system associated with said electric water heater to prevent the risk of bacteria transfer to said hot water distribution conduit, said system comprising an electric water heater having a water holding tank, said water holding tank having a domestic water supply inlet conduit to release water under pressure in a lower portion of said water holding tank, two or more resistive heating elements secured to said water holding tank to heat water in an upper and lower region of said tank, a hot water supply outlet conduit secure to said upper portion of said tank to supply hot water to said hot water distribution conduit, a temperature responsive shut-off valve having an inlet end secured to said hot water supply outlet conduit, said temperature responsive shut-off valve having an outlet end secured to said hot water distribution conduit, said temperature responsive valve having a closure component which automatically closes upon detecting a predetermined low water temperature fed to said inlet end of said valve upon detection of a predetermined water temperature at said inlet end of said temperature responsive shut-off valve, and wherein said temperature responsive valve is controlled by a programmable controller having a memory in which is stored an inputted programmed function to cause said controller to execute the operation of said temperature responsive shut-off valve in response to detected water temperature compared to stored reference temperature values of water in said upper region of said water holding tank and fed to said inlet end of said temperature responsive shut-off valve, and a temperature sensor secured to said upper region of said water holding tank for feeding to said controller said actual temperature signals indicative of said water temperature in said upper region of said water holding tank for comparison to said stored reference temperature value, said controller being further provided with a timer circuit, said controller automatically activating said timer circuit when said controller causes said shut-off valve to close upon detection of said predetermine low temperature value, said controller automatically causing said shut-off valve to open after the expiration of a predetermined time delay by said timer circuit and at which time delay said water temperature in said upper region of said water holding tank is at said predetermined low water temperature.
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