34 Pa. Code § 3a.143 – Cast iron boilers.

(a) The maximum allowable working pressure on the shell of a cast iron boiler may not exceed 15 psig for a steam boiler and the stamped working pressure for a hot water boiler.
(b) The maximum allowable working pressure for a boiler having a cast iron shell or heads, and steel or wrought iron tubes may not exceed 15 psig for a steam boiler and the stamped working pressure for a hot water boiler.

This section cited in 34 Pa. Code § 3a.3 (relating to scope).