N.Y. Comp. Codes R. & Regs. Tit. 12 §§ 4-5.6
Each steam boiler shall have a steam gage connected to its steam space or to its water column or to its steam connection. The gage or connection shall contain a siphon or equivalent device which will develop and maintain a water seal that will prevent steam from entering the gage tube. The connection shall be so arranged that the gage cannot be shut off from the boiler except by a cock placed in the pipe at the gage and provided with a tee or lever handle arranged to be parallel to the pipe in which it is located when the cock is open. The connections to the boiler (except the siphon, if used) shall be not less than 1/4 inch standard pipe size, but when steel or wrought iron pipe or tubing is used, they shall be not less than 1/2 inch inside diameter. The minimum size of a siphon, if used, shall be 1/4 inch inside diameter.
N.Y. Comp. Codes R. & Regs. Tit. 12 §§ 4-5.6