This section is from the book "A Treatise On Architecture And Building Construction Vol4: Plumbing And Gas-Fitting, Heating And Ventilation, Painting And Decorating, Estimating And Calculating Quantities", by The Colliery Engineer Co. Also available from Amazon: A Treatise On Architecture And Building Construction.
192. Fig. 73 represents the building and fixtures already shown in Plan No. 2, along with a system of piping for the supply and distribution of hot and cold water, the supply being taken from the city mains. The minimum pressure in the mains must be more than that required to just raise water to the highest fixtures. With this system of piping, when the street mains are shut off, the entire building will immediately be without water, the boiler of course remaining full, if unsiphoned. The street service pipe a which joins the city main to the pipes in the building has a stop and waste cock b attached on its end just inside the cellar. A water meter c fitted with an air chamber near its inlet indicates the quantity of water used in the building. The pressure in the street mains in this particular case is supposed to be too great for safety or comfort if applied to the plumbing in the building; consequently, a pressure-reducing valve d is placed on the house service pipe, just inside the pipe e which supplies a hose bibb in the front area with water under the full pressure of the main. The stop and waste cock shown on this pipe is to shut off and drain the area pipe during cold weather.
Let us suppose that the average main pressure is 95 pounds by the gauge, and that we reduce this pressure, by the use of the valve d, to a constant pressure of 45 pounds within the building; then the size of the pipes may be approximately as marked on the drawing. The hot and cold distributing pipes are galvanized iron or brass, and some of the branches are shown of lead.
Since the pressure-reducing valve is similar to a check-valve, a safety valve is placed upon the boiler as shown at f, and a pipe g leads any blow-off from f into the kitchen sink. A few lever-handle stop and waste cocks are placed upon the most important parts of the system to facilitate shutting off sections, for repairs, etc., without shutting off the entire building. Each closet tank may be shut off separately, because the ball-cocks or the tank valves in them generally require repairs more frequently than other parts of the system. The boiler and the waterback h furnish hot water for the entire building. It will be observed in this drawing that there is no circulation of hot water between the boiler and the fixtures, and that a considerable quantity of cold water must be drawn from some of the fixtures before the hot water flows. Air chambers i, i, etc. are attached to the piping to prevent water hammer.
The sediment pipe j joins the kitchen sink trap on the house side of the seal. The piping in this sketch is exaggerated in size, and to the eye may appear out of proportion with the fixtures. This, however, was done to show the pipe connections clearly. The inside diameters of the pipes are marked on the drawing.