The maximum allowable working pressure on the shell of a nonstandard riveted heating boiler shall be determined in accordance with Item 3 covering Existing Installations, Power Boilers, except that in no case shall the maximum allowable working pressure of a steam heating boiler exceed 15 psig, or a hot-water boiler exceed 160 psig or 250 °F temperature.
15 Miss. Code. R. 10-76-3.2.2