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Hot Water Suply
47. Expansion of Hot-Water Pipes.—When running hot- water supply pipes, provision should always be made for the expansion and contraction due to the variation of the temperature of the water. If this provision is omitted, the joints are liable to become leaky from the enormous stresses to which the lines of piping will sometimes be subjected. Hot-water pipes should never be embedded in concrete, as the expansion will either crack the concrete or burst the pipes. When pipes must pass through concrete, a little tunnel or duct should be formed to receive the pipe, which can then freely expand or contract.
Installation Of Hot-Water Systems
48. Street-Pressure Hot-Water Supply System.—Fig. 20 gives a sectional view of a building, showing fixtures and 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 exceed that required to just raise water to the highest fixtures. With this system of piping, when the water is shut off the street mains the entire building will immediately be left without water, the boiler, or tank, 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-cock b attached to it just inside the basement. A water meter c 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 beyond the pipe e, which supplies a hose bibb in the front areaway with water under the full pressure of the main. The stop-and-waste shown on this pipe e shuts off and drains it during cold weather.
49.Suppose that the average main pressure is 95 pounds by the gage and that this pressure, by the use of the reducing valve d, Fig. 20, is reduced to a constant pressure of 45 pounds in the basement of the building; then the size of the pipes may be about as marked on the illustration. Hot and cold distributing pipes are of galvanized iron, brass, or copper, preferably of brass or copper suitably annealed.
Since the pressure-reducing valve is similar to a check-valve, in that it prevents the expansion of water back into the mains, a safety valve / is placed on the storage tank. The water in this tank is warmed by the heater g. Lever-handle stop-and- waste cocks are placed on the most important parts of the system to facilitate shutting off sections for repairs, etc.. without shutting off the entire building.
