Fig. 96 shows the distributing lines of a lead-supply tank installation. A is the pipe leading from the tank to the reservoir, the cold for bathroom being branched from it above. B is the main hot service. D and E are range connections. F is a brace supporting the ring under the reservoir. The main stops are within reach from the floor. C supplies a hall lavatory, and also acts as a drain for the main lines. The arrangement permits supplying either hot or cold water to the little hall lavatory; and a cock at the lowest point in C enables the whole combination to drain through it when necessary. By reason of addition of fixtures, incrustation, or other sufficient cause, supplies sometimes fail to give water rapidly enough. This can be remedied by attaching a closed cylinder, and feeding from it. The pressure will fill the cylinder more or less when water is not being drawn, so that it will flow in abundance when a faucet or valve is opened.

Fig. 95. Essential Connections of a House Tank..

Fig. 98. Distributing Lines of Lead Pipe for a Tank Installation..

If the regular supply is dropped into a cylinder, a separate feed pipe is necessary. If the fixture line is large enough, the cylinder may be placed at the upper end, and a check-valve below the lowest fixture to retain what enters the cylinder. Then, when a faucet is opened, the cylinder fur-nishes the water until it is exhausted or the street pressure supplements or overcomes the downward flow. Where the street pressure is not sufficient to reach upper floors, trouble is often experienced in pumping to the tank, on account of the service being too small to fill the cylinder of the pump at ordinary speed. This can be overcome by placing a pocket or sort of air-chamber in the service, and connecting the pump suction to it. The influx of water to the pocket is constant, and the suction of the pump intermittent; hence the full, unchecked capacity of the service pipe is available to the pump. The air-chamber feature permits the water to leave the pocket easily. It is proper to place a check-valve on the house side of pump connection, to avoid annoyance from air when faucets used directly are opened.

Fig. 97. Double-Reservoir Installation for Heating Combined Direct and Tank Supply. Reservoir Consists of Two Concentric Cylinders, Outer One (Direct) being Connected to Water-Back, and Inner One Heated by Conduction..

Another problem of inadequate street pressure where part of the house is supplied from a tank, is the heating of the water of both systems. Only large hotel ranges maintain two fires; and there is not ordinarily room for two heaters in one firebox without interfering with the fire or with the baking properties of the cooker; and mixing the supplies is prohibitive. The difficulty has been overcome in two ways. In one, a double reservoir is used, the high pressure (water from the tank) being turned into the inner one, which is concentric with the outer. A job of this kind is illustrated in Fig. 97. The room required for one reservoir is thus saved, and no extra water-back or secondary heat is necessary. One set only of range heater connections are made - to the outer reservoir. The inner reservoir being entirely encased by the water of the outer one, the heating of the water in the inner one is accomplished by conduction only. The range heater might be connected to the inner reservoir; but the surface for conduction would be the same, and much heat, of the limited supply due to conduction, would be radiated from the walls of the outer reservoir. The high pressure might also be connected to the outer reservoir; but greater care in providing against the possibility of the inner one collapsing would be necessary, as it is or should be made of copper. In double-reservoir jobs, a connection, with check-valve, from the street cold to the tank cold, is made at the reservoir. In this way, if the tank should become empty, the street pressure opens the check-valve without attention, and keeps the inner reservoir filled, and of course supplies automatically any fixture on the high-pressure system that the street pressure will reach.

A second plan of heating the water of both systems, also by conduction, is to use two independent reservoirs. The system requiring the greatest amount of hot water is given a direct connection to the heater, and a secondary heater for warming the water of the other system by water is interposed in the upper pipe of the connections leading to the firebox. The secondary heater has a series of channels or cells, all connecting and pressure-tight and provided with openings for pipe connection. The water of one reservoir is connected to the cell spaces in the secondary heater, just the same as though it were in the firebox; and the water of one system is in that way heated by conduction, by circulating the heated water of the other system about it as it passes from the range heater to its reservoir.

The third method of providing double-boiler service is shown in Fig. 98. Referring to the engraving, A is a l 1/4-mch pipe, leading directly to the tank, and bending over the top. It is connected to a pump in the basement. B is the main supply from the street, to which pipe A is connected at a lower point. No. 2 is a check-valve placed in the main street supply for the purpose of preventing the pump from drawing water from the street-pressure reservoir while pumping water into the tank in the attic. This might occur for various reasons if a check-valve is not used, and would certainly result in case the pump should be operated while the street supply was shut off. Check-valve No. 2 also prevents the tank water from going into the street pipe when both systems are working under high pressure. In practice, a drain-cock should be placed in pipe B above check No. 2. C is the main cold supply, leading directly from the tank to the kitchen, without branches to fixtures at any point. It connects above check-valve 3 to a pipe leading to the tank-pressure reservoir. From the lower end of check 3, a pipe leads over to the main cold supply B. The superior pressure of the tank system keeps check 3 closed, so that water cannot enter the tank system or reservoir from the street while there is pressure upon it from the tank supply. However, immediately upon the tank becoming empty, or its pressure shut off at cock No. 9, the pressure falls in the tank-system pipes until the pressure is inferior to the street pressure, and check No. 3 opens upward and allows the street pressure to keep the tank-pressure reservoir filled. Otherwise trouble might possibly result, but it is not so probable as in jobs having one reservoir within the other. This check admits of both reservoirs filling without having water in the tank when the job is first started; and although it is a minor point to speak of, it is best to be prepared for accidents.