water piping presents a high frictional resistance to the flow of water. The friction losses are so great that the water pressure is cut down rapidly in the distribution system and the delivery of water to the fixtures is unsatisfactory. Frictional resistance is increased by corrosion which roughens the pipe surfaces and fills them with rust.

If the water distribution piping of a building is of good material and well proportioned, the use of water at one fixture will not prevent water from being drawn from another fixture fed by the same pipe. In order to ensure adequate flow, however, losses of head in passing through gates, valves, meters, fittings, and faucets must be taken into account as well as losses in the pipes proper. Piping that is too small requires high velocities of flow which make the operation of water pipes noisy and cause water hammer that jars the pipe in its support. Frequently rapid opening and shutting of valves also cause water hammer.

The use of improper fixture equipment that demands rates of flow in excess of those which the distribution piping can supply is another frequent cause for complaints of low water pressure. Flush valves, for example, are being used more and more instead of ball cock tanks to flush water closets. They demand water at a rate (about 30 gallons per minute) many times greater than needed to fill a ball cock tank in a reasonable length of time and must be fed by large service pipes, meters and distributing pipes in order to operate satisfactorily. It is not economical, however, to use large pipes and equipment in order to meet the requirements of only one or two fixtures. Devices such as flush valves should only be used, therefore, under direct pressure when the sizes of service and distributing pipes required for the general uses of the building are sufficiently large. If installed in small dwellings which are normally equipped with small piping, they should be connected to auxiliary storage tanks. These may be either of the pressure or gravity tank variety.

Plumbing regulation

Good plumbing is a matter that concerns the public health. The regulation of plumbing is therefore justified under the police power. This principle has long been recognized and in many places regulations governing the installation of plumbing systems have been

established by law. In general, however, plumbing regulations only cover the drainage system, of buildings, for the first plumbing regulations were promulgated at a time when physicians and sanitarians were still believers in the sewer-gas theory of diseasenamely, that certain diseases were caused by the escape into dwelling houses of foul air from the sewers and house drains. We know today that infectious diseases are not caused by sewer gas, but we appreciate at the same time that poor house drainage will give rise to insanitary conditions and may result in the spread of disease through cockroaches and other vermin.

The Sub-Committee on Plumbing of the Building Code Committee of the United States Department of Commerce adopted the viewpoint that plumbing regulation should cover the water distribution as well as the drainage system and has formulated the following minimum recommendations for dwellings and similar small buildings.

Article VI.-Water supply and distribution

SEC. 70. Quality of water.

accepted standards of purity.

The quality of the water supply shall meet

SEC. 71. Distribution. The water supply shall be distributed through a piping system entirely independent of any piping system conveying another water supply.

SEC. 72. Water service. The water-service pipe of any building shall be of sufficient size to permit a continuous ample flow of water on all floors at a given time.

SEC. 73. Water supply to fixtures. All plumbing fixtures shall be provided with a sufficient supply of water for flushing to keep them in a sanitary condition. Every water-closet or pedestal urinal shall be flushed by means of an approved tank or flush valve of at least 4 gallons flushing capacity for waterclosets and at least 2 gallons for urinals, and shall be adjusted to prevent the waste of water. The flush pipe for water-closet flush tanks shall be not less than 14 inches in diameter, and the water from flush tanks shall be used for no other purpose.

No water-closet or urinal bowl shall be supplied directly from a water-supply system through a flushometer or other valve unless such valve is set above the water-closet or urinal in a manner such as to prevent any possibility of polluting the water supply.

SEC. 74. Size of water-supply pipes. The minimum size of water-service pipes from the curb to the dwelling shall be inch, and to fixtures as follows:

Sill cocks..

Hot water boilers.
Laundry trays.

inch

SEC. 75. Water supply control. A main shut-off on the water supply line shall be provided near the curb. Accessible shut-offs shall be provided on the main supply line just inside the foundation wall for each flat or apartment of a building, for each lawn sprinkler, for supply to each hot water tank, and for each water closet.

SEC. 76. Water-supply pipes and fittings: Material. All water-supply pipes for a plumbing system shall be of lead, galvanized wrought-iron, or steel, brass, or cast iron, with brass or galvanized cast iron or galvanized malleable iron fittings. No pipe or fittings that have been used for other purposes shall be used for distributing water.

SEC. 77. Water supply, protection. All concealed water pipes, storage tanks, flushing cisterns, and all exposed pipes or tanks subject to freezing temperatures shall be efficiently protected against freezing.

SEC. 78. Relief valves. Wherever a check valve is installed on the coldwater supply pipe between the street main and the hot-water tank there shall be installed on the hot-water distributing system a suitable relief valve.

SEC. 79. Pumps and hydrants. All pumps and hydrants shall be protected from surface water and contamination.

Bibliography

(1) Recommended Minimum Requirements for Plumbing in Dwellings and Similar Buildings. United States Department of Commerce. Elimination of Waste Series. Washington. Government Printing Office, 1924.

(2) Report of the Special Plumbing Board of the Massachusetts Department of Public Health. Boston, 1920.

(3) The Need of Uniformity in Plumbing Regulations. George C. Whipple. Jour. N. E. Water Works Assn., 35, 2, 1921, p. 117–122.

(4) The Flush Valve. Gordon M. Fair. Jour. N. E. Water Works Assn., 35, 2, 1921, p. 137-150.

(5) Principles and Practice of Plumbing. J. J. Cosgrove. 3d edition. Technical Book Publishing Co., Scranton. 1922.

(6) Standard Practical Plumbing. R. M. Starbuck. Norman W. Henly Publishing Co., New York.

(7) The Prevention of Corrosion in Hot Water Supply Systems. C. R. Texter. Jour. Amer. Water Works Assn., 10, 1923, p. 764–772.

(8) The Water Supply, Sewerage, and Plumbing of Modern City Buildings. W. P. Gerhard. John Wiley & Sons. (1910?)

(9) Water Hammer. O. Simin. Proc. Amer. Water Works Assn., 1904, p. 341.

1 Lead-lined, cement-lined, tin-lined and copper pipe may also be included in this list.

CHAPTER XVIII

CORROSION OF PIPES

Corrosion is a process or combination of processes by which metals wear away. Two causal factors are requisite to corrosion: moisture or water, and air or oxygen. In the absence of moisture metals do not corrode; in the absence of oxygen they are attacked but slightly. The corrosion of metals usually covers them with deposits or incrustations of the metal in altered form (rust).

Water pipes are subject both to internal and external corrosion. The latter is sometimes the more serious of the two. Corrosion, more than any other factor or combination of factors, determines the efficient life of water pipe. In metal pipes corrosion disirtegrates the metal and reduces the wall thickness; in wood pipes it rusts the metal bands; in reinforced cement or concrete pipes it attacks the reinforcing wherever it is insufficiently protected.

The efficiency of water pipes varies with their carrying capacity and tightness. New smooth pipes convey more water under a given head than old rough ones. In time, corrosion "eats" through the pipes in places. They begin to leak and water is wasted.

The quality of pipe service depends upon the ability of the pipe to deliver the water to the consumer in the condition received. In flowing through a long pipe, water comes into contact with many metals and other materials. The metallic compounds worn away from the pipe surfaces by corrosion may dissolve in the water or be carried away in suspension.

Causes of corrosion

Corrosion is a surface phenomenon. Its causes are electrochemical in nature: chemical because corrosion is due to reactions of the metal with different elements or compounds in the water; electrical, because these reactions require a concurrent interchange of electrical charges. The theories by which corrosion may be reasonably explained are discussed below. Three main types of corrosion occur in water pipes: self-corrosion, galvanic corrosion, and electrolytic corrosion.

Self-corrosion. The most general type of corrosion is known as self-corrosion and takes place when a metal is brought in contact with water containing oxygen.

The tendency of metals and other solids to go into solution varies greatly. This is illustrated in the following table which shows the more common metals arrayed according to their "solution pressure." Each metal has a greater tendency to dissolve than the succeeding ones. Zinc, for example, has a higher solution pressure than iron, iron than lead, and lead than copper. The order of the elements in this table is not alone the order of their solution pressure, but, since, as we shall see later, solution of metals is the result of electro-chemical activity, it is also the order of electrical and chemical activity of the elements. Each metal is said to be more active, or electro-positive, than the succeeding ones.

When a single metal, such as iron, is immersed in water free from impurities, including oxygen, it exerts its solution pressure by discharging into the liquid a certain number of electrically charged particles called ions. These metal ions carry a charge of positive electricity and therefore increase the positive electricity of the water while decreasing that of the metal which becomes negatively charged. The electrical balance is upset, the water has too much positive electricity, the metal too little. Equilibrium is regained, however, by the displacement from the water of an equivalent number of positively charged ions which migrate to the metal. These ions are hydrogen iors, the only positive ions that are present in pure water. Pure water is not an inert substance consisting of molecules of H2O. It has the power of dissociation and contains in addition to molecules of H2O a number of unassociated hydrogen ions (H) and

1 1 Solution pressure is tendency to dissolve.