that of the local electric lighting system. For example, they recommend that two 2300-volt transformers be connected in series on a 2300-volt line and the 110-volt windings be connected in parallel with each other, thus giving about 55 volts on the cables to be attached to the service and hydrant. For a main 6 inches or more in diameter, both the primaries and secondaries can be connected in parallel, giving 110 volts.

Distribution transformers suitable for this work are usually kept. in stock by electric lighting utilities, so there is rarely any reason for a water department to buy them. Inasmuch as the connections with lighting circuits should be made only by employees of the electric utility, such an electrician should be a member of each gang using one of these transformer outfits. Present practice is for the water department to hire the equipment and electricians from the lighting utility as needed and add a water works foreman and laborers. Where such an outfit is used the electricians should be .carefully instructed regarding the danger of using heavy currents.

When such equipment is connected to the lighting circuit and the frozen service, it will thaw the pipe just as quickly as a selfcontained outfit will do the work. Its drawbacks are the time needed to make the connections with the lighting circuits in some cases and the occasional impracticability of making any connection at all. It is so effective, however, when properly used, that wherever emergency equipment is likely to be useful, it is advantageous to have it in readiness by mutual arrangement between the water and electric lighting officials, before severe cold weather arrives.

Thawing hydrants and their branches, like thawing large mains, requires equipment of greater capacity than is needed for thawing service pipes. When the work is done by steam, an upright boiler is generally used; sometimes an old fire engine is available for the purpose. The steam is delivered through a hose into one of the nozzles of the hydrant. If the branch is frozen, it is usually necessary to remove the hydrant and insert the steam hose into the end of the branch. Where a hydrant branch has once been frozen, the hydrant pot and branch should be lowered if this is possible. If the trouble is in the barrel, above the bottom valve, denatured alcohol or some other anti-freezing substance should be placed in the barrel.

When the hydrant and its branch are thawed electrically the currents are so heavy that only a thoroughly competent, careful electrician should be in charge of the electrical part of the work. In fact, wherever electrical thawing is practiced, care must be taken to prevent any annoyance to the public by straying currents and the danger of causing a fire hazard or of damaging pipes, particularly pipe joints, by excessive currents must never be overlooked.

CHAPTER XVII

PLUMBING IN RELATION TO WATER SUPPLY

The "plumbing" of a building, as the term is commonly used, includes the pipes for distributing the water supply, the fixtures for using water, and drainage pipes for removing waste water and sewage, together with fittings and appurtenances of various kinds, all within or adjacent to the building. The "service pipe," which forms the connection between the water main and the building, and the "house sewer," which conveys waste water and sewage from the building to the street sewer or other point of disposal, are included in the "plumbing system" of a building, using the term in a broader sense. Connections for rain water are also included, if the water is discharged through a house sewer or a house drain.

Plumbing and water quality

The quality of the water delivered by the street mains to the service is often markedly changed by the time the water flows from a faucet of the house distribution system to fill a drinking glass, a wash bowl, or a bath tub. The elements of a lead poisoning are not usually picked up in the street mains but in service pipes and distribution systems of house plumbing. The rust of the "red water plague" is not produced in distribution systems but in water backs of kitchen stoves, storage tanks of hot water systems and hot water piping of buildings.

Plumbing materials vary greatly in their resistance to corrosion. Cheap plumbing naturally corrodes more quickly than materials of good quality. It is also true that plumbers often do not appreciate the serious objections to the use of dissimilar metals in contact. This stimulates galvanic corrosion, the effects of which are illustrated by the familiar slug of red water discharged when a brass faucet attached to an iron pipe is first opened. At fittings corrosion is furthermore accelerated by the exposure of unprotected metal along threaded joints. Galvanized pipe, for example, is deprived of its protective zinc coating at the threads and the un

protected metal corrodes rapidly. High velocities of flow and high temperatures also render water more active. The "red water plague" is chiefly a hot water problem.

Although it is possible to reduce troubles caused by the corrosion of house plumbing systems, by employing water piping materials that experience has shown to be adapted to the nature of the water, even the best selected materials cannot be expected to withstand the corrosive properties of some waters. Water supplies, therefore, should be so chosen or so treated as to reduce the aggressiveness of the water to the lowest degree that is economically obtainable. The hot water systemis of large buildings are sometime protected against corrosion by physical or chemical treatment of the water before passing it into the distribution system. There are several types of apparatus on the market that accomplish this treatment. They are known as "deactivators," "degasifiers," etc. It sometimes happens that hot water is discharged back into the water mains from domestic hot water systems. In separate dwellings, there are two methods of supplying hot water, known as the "tank system" and the "pressure system." In the tank system the water to be heated is received from an open tank in the attic which is supplied with water from the mains through a ball cock inlet. This separates the domestic hot water system from the cold water direct pressure piping. The tank also serves to take care of the expansion of the water during heating, the escape of air liberated by heating, and the escape of steam generated when the hot water boiler becomes overheated. With this system there is no chance of discharging hot water into the mains. In the pressure system, on the other hand, the heating equipment is connected directly to the house pressure piping. Unless a pressure relief valve is provided on the boiler, no means of escape exists for the air and steam that are driven off when the boiler becomes overheated. When this happens, the pressure developed in the hot water system overcomes the water supply pressure and forces hot water through the service connection back into the street main and may damage the meter. In order to prevent the discharge of hot water in this manner, check valves are frequently inserted in the cold water connections to the boiler and close this avenue of pressure relief. Boiler explosions are then apt to occur and become dangerous to life and property. Hot water pressure systems

should, therefore, be equipped with pressure relief valves. These are commonly attached to the hot water boiler and automatically relieve the pressure created when the boilers are overheated. In most cases overheating may be ascribed to unregulated gas heaters.

Plumbing and water consumption

The arrangement of the plumbing system has an important bearing on the consumption of water and the amount of waste. This is a matter of public as well as private interest, although it is sometimes difficult to distinguish between legitimate and wasteful use. The present tendency in house plumbing is to call for large streams of water delivered rapidly. Faucets for supplying water at sinks and basins are often too big and waste much water. Bath tub faucets, on the other hand, may be large without resulting in waste, because the object of such faucets is to fili the tub rapidly and the outlet is usually closed when filling begins. Bath tubs, however, are less sanitary than showers and probably also less economical in the use of water.

Water supply pipes are often installed without due regard to their protection against freezing. The danger of freezing induces householders to let faucets run over night during cold weather. Attempts of this kind to prevent the freezing of exposed pipes result in the waste of large volumes of water.

Hot water pipes are frequently run too close to cold water pipes and heat the water in the latter. Faucets must then be left running for a long time before they discharge cold water. The use of cheap plumbing which wears out rapidly and is often left unrepaired is another factor in the consumption of water. Leaky faucets. waste much water and broken or unadjusted ball cocks for water closet tanks sometimes discharge large volumes of water unnoticed or without an attempt being made to correct the trouble.

Plumbing and water pressure

When the supply of water at fixtures is inadequate, it is common for the occupant to complain to the water department that the water pressure is too low or that the service pipe from the street main to the house is too small. The real cause of the trouble is often to be sought in the house plumbing system. Small or cheap