TYPES OF WATER SUPPLY There are various ways in which it may be necessary to obtain the water supply for a building. The usual course in cities and towns is to employ the Municipal Water Works service. This, of course, settles the supply feature, and the plumber simply provides the house and yard pipe, i-inch or larger main, according to the character of the work. If of lead, the pipe must be of strength according with the pressure. Any of the light-weight grades of lead supply will stand 1,000 pounds per square inch for a short time; and the usual strength used on 50 to 80-pound pipe will not burst under 1,400 to 1,600 pounds when new and un strained. Under constant pressure, the enormous strain possible from water-hammer, and general deterioration from use, make it advisable to employ pipe which, when new, is 20 times as strong as that necessary to contain the pressure. No attention is necessary as to the strength of zinc-coated or tin-coated iron pipe; it will stand any pressure ordinarily encountered.
The two general methods of supplying buildings with water are: (1) the direct system; and (2) the indirect or tank system. The direct method, generally employed in cities, places each fixture connected with the supply under the same pressure as the street main, unless a reducing valve is introduced, thus often subjecting the work to need less high pressure and always to the widely varying conditions and quality of service incidental to such use. In the direct system it is
good practice, where at all practicable, to pipe and fit the work gener ally for pressure not exceeding 50 pounds per square inch, and then use a reducing valve to maintain such pressure as is required.
The indirect method is almost always necessarily employed in isolated work; and even where municipal service is available, it is generally better for ordinary domestic purposes. With the indirect system, the connection with the street main is carried directly to a tank placed in the attic, or at some point above the highest fixture, as shown in Fig. 51. The supply to tank is regulated by a ball-cock which automatically shuts off the water when the tank becomes full. and opens and refills it again when water is drawn out. All the plumbing fixtures are supplied directly from the tank, and are there