This section is from the book "The Building Trades Pocketbook", by International Correspondence Schools. Also available from Amazon: Building Trades Pocketbook: a Handy Manual of reference on Building Construction.
The source of supply of water to a building will depend upon prevailing conditions and the location of the building. City buildings are usually supplied from city mains, while country buildings are supplied from wells, lakes, and streams, by means of pumps, hydraulic rams, etc.
House pipes should connect to the mams by corporation stops. A stop and waste should always be placed under the sidewalk at the curb, and also a separate stop and waste upon the service pipe just inside the cellar wall.
If the street pressure is great enough to force water to the top floor of a building, all fixtures are usually supplied with both hot and cold water, by street pressure. If the pressure is too low, or the supply intermittent, a tank is placed in the attic to supply the building. If the pressure is too high, it is customary to apply a pressure regulator in the cellar.
The sizes of street service pipes depend chiefly upon the street pressure and the size of building to be supplied. The following is common practice:
Class of Building.
Size of Pipe. Inches.
Single dwellings, two or three stories high
1/2 or 3/4
1 or 1 3/4
Tenement buildings and apartment houses
1 1/2 or 2
Hotels and factories.........................................
2 and up
These pipes should be increased one rise if pressure is low.
The amount of water raised by single-acting pumps is estimated by multiplying the number of strokes which the piston travels in one direction per minute by the volume displaced or traversed by the piston in a single stroke, the supposition being that the water flows into the pump barrel only when the piston ascends. It has been found, however, that the column of water does not cease flowing when the piston descends, and that the amount of water delivered is greater than usually supposed; in some cases, it is nearly double the theoretical amount.
A column of water 34 ft. high is balanced by the pressure of the atmosphere, but in practice it requires a very good pump to draw to a height of 28 ft.
The height to which hot water can be raised by suction is much less than that of cold water, the height varying with the temperature. This is due to the increased pressure of the vapor. Where possible, the hot water should flow into the pump by gravity. The following table gives the maximum vertical heights of suction pipes for different temperatures:
Absolute Pressure of Vapor.
Vacuum. Inches of Mercury.