49 C.F.R. § 230.51 Number and location.
Title 49 - Transportation
Every boiler shall be equipped with at least two water glasses. The lowest reading of the water glasses shall not be less than 3 inches above the highest part of the crown sheet. If gauge cocks are used, the reading of the lowest gauge cock shall not be less than 3 inches above the highest part of the crown sheet.
Title 49: Transportation
PART 230—STEAM LOCOMOTIVE INSPECTION AND MAINTENANCE STANDARDS
Subpart B—Boilers and Appurtenances
Water Glasses and Gauge Cocks
§ 230.51 Number and location.
