objection to the use of this crude form of cut-off is that confusion may result from the use of valves. In Fig. C a patented form of cut-off is shown, in which this trouble is not present. By throwing the lever up or down either tank or street pressure is turned on. HEADERS In large hot-water supply systems the cold-water lines connect into a header, the hot-water lines into another, and the circulation. pipes into another. This makes the work very systematic and easily cared for. Fig. D shows the general arrangement of a header, with its branches, each supplied with a shut-off, and each branch also provided with a drip connecting into a main drip, the latter emptying into an open fixture. The same general arrangement of headers, branches, drips, valves, etc., may be, and often is, employed to great advantage in connection with the hot- and cold-water supply of a residence. In connection with high-grade residence work, a very neat and artistic piece of work can be performed on these headers by using polished brass pipe and fittings, and additional neatness in appearance may be obtained by bending the pipes at changes in direction, instead of performing the work with fittings. Better results can also be obtained from this method for the reason that there is less friction encountered in smooth bends than in bends made with fittings. The employment of these methods is almost a necessity on large work, as in such work the supply piping is of such a complex nature that it cannot safely be installed other than in the most systematic manner. IN the supplying of hot water for large buildings the boiler is generally of the horizontal style, hung by wrought-iron hangers from the cellar timbers, although vertical boilers are sometimes used. The source of heat for such boilers is generally a special tank heater. Live and exhaust steam are also much used by means of steam coils placed inside the boiler. A combination often used to advantage includes both tank heater and steam coils, the heater being used during the summer and the coils during the winter season, when the heating. plant of the building is in operation. The use of the tank heater and steam coil is seen in Fig. D, Plate 54. In addition, special heating devices or auxiliaries are used in this work, one of them, known as the P. P. Heater, being shown connected to the boiler in Fig. E, and a sectional view of the same in Fig. F, Plate 54. As seen from the latter, the device consists essentially of three pipes, one inside the other. Cold water is conducted through the innermost pipe, from which it passes into the pipe or tube next outside, this pipe being closed at its end. Steam is conveyed into the space between the middle pipe and the outer one, thus entirely surrounding the cold water that enters. The flow connection is made to the middle pipe, also the drawoff connection. It is claimed that the heating of water by means of this heater is very rapid, and that even in the form of steam vapor it will heat the water more rapidly and in greater quantity than it can be heated by a water front with a hot fire. The heater may be connected with the steam piping of the building, as shown in Fig. E. The heater is made in several sizes, ranging from the kitchenboiler size to sizes suitable for large work. The size of hot-water boilers naturally depends on the character and use of the building, the number of apartments, and number of fixtures supplied with hot water. In the case of apartment buildings it is generally a comparatively simple matter to approximate the boiler capacity necessary, but in the case of many buildings, experience and judgment are necessary in arriving at a proper size. |