Miniature boilers shall be provided with at least one feed pump or other feeding device, except where it is connected to a water main carrying sufficient pressure to feed the boiler or where it is operated with no extraction of steam (closed system). In the latter case, in lieu of a feeding device, a suitable connection or opening shall be provided to fill the boiler when cold. Such connection shall be no less than one-half inch NPS for iron or steel pipe and one-fourth inch for brass or copper pipe.
229 Neb. Admin. Code, ch. 23, § 009