Feedwater connections shall be independent of any water gage connections. Feedwater connections for cast iron steam boilers, when introduced from a pressure line, shall be made to the condensate return line or the reservoir of the condensate return pump, not directly to the boiler. There shall be a check valve in the feedwater line at the boiler for all boilers.
N.Y. Comp. Codes R. & Regs. Tit. 12 §§ 4-5.9