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must be put up so that the angles and bends are free to move a little, or else the expansion and contraction will strain the fittings and produce leaks. The effect which the water will have upon the pipes is a matter which should be considered, but it can be determined only by local examination, and recommendations as to the use of piping must be made with reference to the analysis of the local water supply. If brass piping is used, it should be semi-annealed and specified as "iron size"; that is, the thickness must correspond to that of iron pipe of similar size, as distinguished from so-called "plumbers' tubing", the use of which is not to be recommended.

Iron Pipes. If the cost of brass piping proves to be excessive, a good quality of iron pipe may be substituted where there is danger of the corrosion of lead or of its bursting by great pressure. Iron pipe may be obtained with a lining of block tin, which forms a pure and very satisfactory channel, or with a less expensive galvanized or zinc coating. The directions given for piping with brass must also be followed in running iron pipe, and, besides, precaution must be taken against condensation which will take place upon iron pipes in warm weather, because of the fact that iron conducts heat so rapidly. This condensation may be so great as to trickle down and cause damage to paper or decorations. Where there is this danger, the pipes should be run in tubes of zinc which will conduct the water to a safe outlet. This precaution should be observed, even in the case of lead or brass piping, when costly decorations or papers are liable to injury from bursting or leaking pipes.

General Rules for Running Pipes. The fastening and joining of all pipes should be carefully watched to see that they are run in straight lines, with free angles. The hot-water pipes should be separated by a little space from the cold-water pipes so that there will be no transmission of heat from the former to the latter. Every. pipe must be run so that it will pitch toward one of the faucets or waste cocks, which must be provided in convenient places and in sufficient numbers to shut off and drain both the hot- and cold-water pipes of any given part of the house, as well as of the whole system.

Waste Pipes and Traps. The waste pipe or outlet of every plumbing fixture must have, as near as possible to the fixture, a trap to prevent foul odors and sewer gas from escaping. The simplest form of trap, and in its improved form one of the best, is the S-trap,

Fig. 54. This consists of a piece of pipe bent into the form of the letter S, with a screw in or near the bottom to permit cleaning out. The theory of this trap is that some of the water which passes through will remain in the trap, as shown in the cut. In actual use, however, if sufficient water runs through to fill the outlet.completely, the falling water will create a vacuum at A, which will cause the outside air to force out the water in the trap until it falls below the bend B, and will thus destroy the seal. A greater danger exists where two or more fixtures are connected with the same soil pipe. In this case, the seal of the lower fixture will be broken by reason of the column of water discharged from the upper fixture. A partial vacuum is created in the soil pipe, and the outer air, rushing in to fill the void. by the easiest way, will force the water out of the trap below, Fig. 55. This is a real danger and should be guarded against.

A

The improved trap which obviates these perils has an inlet at the highest point of the trap, A. The vacuum in the outlet pipe will be filled from this source without disturbing the water in the trap. This inlet pipe must, of course, be carried to some main air pipe; it is therefore, customary to run beside the main soil pipe a line of vent pipes to which the different trap vents are attached, the main vent usually starting from the base of the soil pipe and entering it again above the highest fixture.

Fig. 54. Section of Plumbing
Showing Use of S-Trap

Another way of guarding against siphonage is to make the trap so large that enough water will drain back from the outlet and sides of the trap to restore the seal. This is called a "pot" or "cesspool" trap. City plumbing laws generally require the venting of traps, and it should be done in all cases.

Testing. When the waste and air pipes are all in place and the connections for the various fixtures are put in, the whole system

should be subjected to an effective test. The simplest and most efficient one to employ at this stage is the water test called for by our specifications, which should be carried out in the presence of the superintendent. It consists in closing all openings in the pipes and filling the whole system with water, either by attaching a hose at the bottom or by filling from the top. If the water does not lower in the pipe after standing ten or fifteen minutes, the system may be pronounced tight. If, however, the water level drops, there is evidently a leak somewhere which must be sought out at once. In a tall line of piping the water pressure will be such that

Fig. 55. Siphonage of Trap

defective joints or sand holes will be discovered by a stream of water, or at least by the trickling of water down the pipe. Imperfect joints in the cast-iron pipes may be remedied by more careful calking, but sand holes cannot be repaired. The defective pipes must be replaced, and the new pipes again tested until the system proves absolutely tight.

After all fixtures are set and all connections completed, another test is usually made. This may be the "peppermint test" or the "smoke test". In the former a vial of oil of peppermint, which is sold sealed for the purpose, is taken to the roof and emptied into the top of the soil pipe. A quantity of hot water is immediately poured in and the top of the pipe closed by stuffing in paper or rags. The vapor, charged with the odor of peppermint, is thus unable to escape and will penetrate the whole system. All drain, air, or waste pipes, and connections are immediately examined and any odor of peppermint detected will be evidence of a defect which must be remedied. Great care must be taken in applying this test. It should be made by separate persons, one outside and one inside the house, and no direct communication should be held until the test is pronounced satisfactory.

Another method of applying the peppermint test is to close all vent pipes and vaporize the oil of peppermint in the receiver of a small air pump, and then to force the vapor into the system under

pressure. The receiver is provided with a gage so that any leak will cause a fall in the mercury and can then be located by the odor of the peppermint.

The smoke test is required in the building of our house. This is made by closing the system as for the peppermint test and forcing into the pipes, by means of a bellows, smoke from oily waste or some similar substance. When the pipes are filled, a slight pressure is produced, which is shown by a float that rises and remains in this position if the joints are tight. If there is a leak, the float falls as soon as the bellows are stopped, and the leak may be located by the issuing of smoke from the joint. Special machines are to be bought for making these tests, which should be carried out in the presence of the architect or superintendent.

HOT-WATER SUPPLY

Attic Supply Tanks. In New England it is customary to supply the bath boiler from a separate tank in the attic, this tank being filled from the regular house service with a ball cock to regulate the flow. The supply from the boiler to the various fixtures is made to return again to the boiler for circulation, which allows hot water to be drawn at once at each fixture. From the highest point of the circulation a small "expansion pipe" is run to the tank and turned over the edge to discharge just above the water line, in order to allow the steam and froth from the boiling of the water to escape into the tank. This tank should be supplied with an overflow to some convenient fixture. Outside of New England, the tank is generally omitted and the boiler filled from the house system, but this requires a strong boiler, usually of galvanized iron, and is not so satisfactory as the expansion system.

Range Boilers. Hot water is usually provided for by connecting the boiler to a water back or heating coil installed in the fire box of the kitchen range, the supply of hot water depending upon the use of the range for cooking purposes. Another method is to install the boiler in the cellar and to connect it with both the furnace and a separate heater. In this case, the continuous furnace fire in cold weather keeps a constant supply of hot water during the winter months, and the piping is so arranged that when warm weather

comes, the furnace can be disconnected and the separate heater used as needed.

Range boilers are made of copper or of plain or galvanized steel, and they may be set vertically or hung horizontally, as the

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location requires. The most common type is the vertical

boiler of from 30- to 60-gallon capacity, set on an iron stand beside the kitchen range, and connected to a cast-iron water back or a pipe coil in the range, Fig. 56. The coldwater supply is piped into the boiler at the top; it discharges near the bottom of the boiler, and passes thence into the water back; there it is heated and returned, either to the boiler by a pipe higher up, Fig. 57, or sometimes to the outlet pipe above the top of the boiler.

Gas Heaters. Where gas is available for heating, one of the various forms of gas heaters may be employed, either alone or in connection with the range, furnace, or other coal fire. The simplest type of heater keeps an ordinary gas flame burning all the time if a constant supply of hot water is desired; or, if the hot water is wanted only periodically, the flame may be extinguished and relighted, as occasion requires.

Fig. 57. Detail of Water Tank Showing Connections

Other types contain automatic devices for regulating the size of the flame according to the use of the water. These heaters usually have a small pilot light which burns when water is not being heated; and the pilot light and burners are so arranged that the opening of a faucet in any part of the hot-water system releases a pressure which opens the gas valve, and lights

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