h. The water piston must be of simple and strong construction, with follower bolts tightly fitted, and with fibrous packing so cut as to prevent by-passing.
i. All materials used in construction of piston, except packing, must be brass, bronze, or other non-corrosive metal.
j. Bushing studs must be of Tobin Bronze, and of such size and number, that the maximum stress at the bottom of the screw thread shall not exceed 10,000 lbs. per square inch, in the event of plunger becoming fast in the bushing with 80 lbs. of steam in the steam cylinders.
k. For each bushing stud there must be provided a composition nut and check nut.
l. All minor parts exposed to the action of water in water cylinder, that are not herein specified, must be of brass, bronze, or other non-corrosive material.
31. Pump Valves.
a. All the suction and discharge valves in any one pump must be of the same size and interchangeable.
b. There must be a clear space around each rubber valve, between it and the nearest valve, equal to at least one-fourth of the diameter of the valve, or between it and the wall of the chamber of at least one-eighth of the diameter of the valve.
c. These valves must be of the very best quality of rubber, of medium temper, with a face as soft as good wearing quality will permit.