Los Angeles Experience With Water Hammer

Abstract

ject of numerous excellent technical papers given before this Association and many engineering societies. The matter has usually been treated on a highly technical level, with many mathematical formulas and graphs based on extensive experimentation. These papers, with their background of study, have been of tremendous value in developing remedies for water hammer and surges in trunk lines and pumping plants. In grid systems with branch lines, services, air valves, blowoffs and the many appurtenant structures, however, the complexity of conditions is such that the small water works operator, who probably is not an engineer, seeks a practical rather than an analytical solution to his problem. With that idea in mind, the subject will be treated in this paper on the basis of practical experience in the control of water hammer and surges in Los Angeles. The water distribution system of Los Angeles is a vast network of different pressure zones, the area served varying in elevation from zero to 1,719 ft. above sea level. If each zone were fed from a tank or reservoir, there would be little trouble from water hammer in the distribution system. This method is impossible for many reasons, however, and a system of pressure regulators is used. The number of service connections per zone ranges from 20 to 150,000, and the 104 pressure-regulating stations vary from one 2-in. regulator to six 20and three 12-in. regulator . Two types of valves are used for regulating water pressures : the globe type and the plug type, operated by a hydraulic cylinder. Experience has shown that the development of water hammer is equally possible with both kinds of regulator. The pilot valve maintains the same control on