This section is from the book "American Plumbing Practice", by The Engineering Record. Also available from Amazon: Plumbing: A working manual of American plumbing practice.
Figure 3 is an isometric general view of the twin 60,000-gallon roof tanks T T, with the tank-house and all pipe connections removed for clearness. Figure 4 is a plan of the tanks and tank girders, and Fig. 5 is an elevation at Z Z, Fig. 4. The tanks are made of 5/16 - inch tank steel.single-riveted,on frames of 2"x2"x 5/14" angle iron, about 24'x10'x6' deep. Each tank has two longitudinal tie-rods and two sets of eight transverse tie-rods, all one-half inch in diameter, and hooked into angle clips. The tanks stand on five rolled-iron I beams 12 inches high, which are framed into similar longitudinal girders B B, resting on wooden cushion sills C C, laid on the main outer wall W, and on special bearing wall V. Beams A A, etc. are connected by 32 small crossbeams D D, etc., which may have been designed to support wooden cushion pieces on their top flanges, or a mass of concrete bedding to afford support for the bottom of the tanks throughout. Light vertical angle and beam posts E E, etc. are riveted to the beams A and B, to support the roof and side frames, which are covered with corrugated iron, and all connected by angle iron. This covering, built after the tanks were finished and connected, is thought to be sufficient, together with the frequent fluctuations of its level, to prevent the water in them from freezing, but the position is very much exposed, and a steam radiator will be put in the house if necessary.
Figure 6 is a view with the supporting beams,floor, and house removed, so as to show the pipe connections clearly. G is the 4 inch delivery from pumps. H the 4-inch house supply, and I the 4-inch fire line. Kisai 1½-inch supply to the hot-water boilers. L is a 1¼-inch supply to the main toilet-room. M is a 1¼--inch supply to the kitchen, and N isa 1¼-inch supply to the laundry. O is a ¾-inch telltale and pressure pipe to the pump governors. The horizontal offsets in the small service pipes were necessitated to avoid the obstructions caused by beams A A, E E. etc. Figs. 3, 4, and 5. P P are 3-inch overflow stand-pipes discharging directly to the roof gutter. V V, etc are ¾-inch vent pipes to facilitate the emptying of the risers when the upper valves are closed. It will be noticed that the valves are arranged so as to permit any service pipe to be connected or disconnected with either or both tanks.