[Code of Federal Regulations] [Title 49, Volume 4] [Revised as of October 1, 2006] From the U.S. Government Printing Office via GPO Access [CITE: 49CFR230.51] [Page 444] TITLE 49--TRANSPORTATION CHAPTER II--FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION PART 230_STEAM LOCOMOTIVE INSPECTION AND MAINTENANCE STANDARDS--Table Subpart B_Boilers and Appurtenances Sec. 230.51 Number and location. 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.