The extraordinary height of many of our office buildings and apartment-houses is such that water forced to a tank at or near the roof and distributed downward has a pressure altogether too great for many of our ordinary plumbing fixtures and for lead pipe of usual thickness.

In the case of the Tribune Building in this city, the height water is pumped is about 170 feet, which to distribute backward again would bring on a fixture in the basement or cellar a pressure of from 70 to 75 pounds per square inch - in itself too much for fixtures, but that, when taken in connection with the "water-hammer," which will be likely to occur, would be almost sure to destroy the strongest made valves, etc.

To obviate this, in the above-mentioned building, Edward E. Raht, the architect, provided an intermediate tank t and placed it midway between the floors on which water-closet and bowl fixtures are used. The plumber who did the work was Alexander Orr, of New York. The cisterns for the water-closets on the fifth floor and all fixtures above them take water from the upper house-tanks (H T), while the wash-bowls on the same floor and all fixtures below them take their supply from the intermediate tank.

The diagram shows the arrangement of the tank-pipes and system generally. The pipe from the Cro-ton main connects with the meter M, and the water is regulated into the lower tank (T ) by a ball-cock; this tank is below the sewer-level and has no overflow. From the receiving-tank the steam-pump (P) elevates the water to the upper house-tanks. These tanks overflow to the eaves-troughs and have no direct communication with the sewers. Tank t takes its supply from the upper tanks and is regulated by a ball-cock; it is also furnished with an overflow-pipe a, whose lower end is carried to the receiving-tank. This is to prevent loss of water should the ball-cock fail. It also acts as a tell-tale. Two house-tanks are used, with a system of change-off valves and an equalizing-pipe. All the tanks are of wrought-iron.

Figure 73.