Section R. 400.18622 - Hot water heaters and storage tanksRule 622.
(1) A hot water heater, other than an electrically heated heater or a booster heater for a dishwasher or for laundry purposes, shall be installed in the heating plant or in an enclosure of like fire-resistant construction and shall not be used for the storage of any combustible material.(2) A hot water storage tank shall be equipped with a safety device that prevents temperatures of more than 210 degrees Fahrenheit and pressures in excess of the maximum working pressure for which the tank is designed from being reached. Any of the following are acceptable safety devices:(a) An acceptable pressure relief valve that is combined with an energy cutoff approved by underwriters laboratories, incorporated, or the American gas association.(b) An acceptable pressure relief valve and an acceptable temperature relief valve of the spillage type.(c) An acceptable combined temperature-pressure relief valve of the spillage type.Mich. Admin. Code R. 400.18622