The Golden State: Where & How to Live, Secure, Visit, Enjoy and Thrive in California
How To Design And Install Plumbing
The piping of the house service must be installed in as direct and short a manner as is practical. Turns, offsets, and traps, should be avoided because these elements create friction and diminish the discharge capacity of the service, Fig. 194.
It is also important that the house service be placed in the ground at sufficient depth to protect it from freezing—four feet is considered adequate. Should it be impossible to place the service water within it was at rest. Should some one suddenly draw water from it, however, a decided drop in pressure would occur at the outlet orifice. The variation in pressure between the main and the outlet end of the water service is referred to as pressure loss by friction. It is logical to assume that the more fittings, stops, and other devices placed on the distribution system the greater the pressure loss, and therefore the lower the discharge capacity of the water service.
Very little reliable information regarding pressure loss through stops and fittings is available. Data largely consist of laboratory conclusions based on tests of short duration. Water usually contains mineral elements which can be removed by centrifugal force. When these elements are precipitated they adhere to the pipe interior. The size of the pipe is decreased materially under these circumstances, and its discharge capacity is tremendously reduced. There may be fluctuations of pressure in city mains caused by emergency draws, peak loads, or breakdown of equipment which also change the situation. However, these are out of control as far as the plumber is concerned and need not be considered in the design of the installation.
Table 12, opposite, indicates the approximate loss of pressure by friction in pipe valves and fittings of various design, and from it the reader can at least realize the necessity of giving this problem some consideration.
Additional pressure may be lost because of the height to which the water must flow; however, pressure loss resulting from elevation is a relatively simple problem. It is a scientific fact that a column of water 1 foot high exerts a pressure of .434 pounds per square inch at its base. This fact simply indicates the weight of a column of water 1 inch square by 1 foot long. The diameter of the pipe has no effect on the pressure at its base. A pressure gauge provided on plumbing installations always indicates the pressure per square inch. If a building is 50 feet in height, the loss because of head would be .434X50 or 21.7 pounds. This amount can be deducted from the original pressure to determine whether or not it is of sufficient force to elevate water to the required height.]
