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How To Design And Install Plumbing

Water, like gases and solids, is composed of small individual parts scientifically referred to as molecules. Each molecule of water consists of two atoms of hydrogen and one atom of oxygen in chemical union in definite weight proportion. The molecules are separate particles and, as such, have distinct properties.

When heat is applied to water, the molecular activity is intensified. Each particle expands in itself and tends to move in a direction opposite to the others. Heat convected into the water increases its volume, because of the expansion of each molecule. A cubic foot of water at 39.1°F. has a specific weight of 62.425. At 62°F. it has a weight of 62.36.

When water reaches the boiling point (212°F.) under atmospheric pressure, it changes character. The molecules have expanded to such an extent that they become lighter than atmospheric pressure. Disintegration occurs, and vapor, referred to as steam, rises from the surface of the water. As the temperature decreases, the molecular activity lessens. Thus the water contracts, attaining its normal density at 39.1 degrees. The boiling point of water is increased tremendously under pressure greater than atmospheric, which fact makes protection of the hot-water distribution system against explosion necessary.

The movement of water in a distribution system is the result of expansion and contraction of the molecules contained in the water. The molecular theory can be applied in its entirety to hot-water service.

STORAGE TANK AND WATER HEATING DEVICES

The hot-water tank serves the domestic hot-water system in a storage capacity, and care in planning is essential in making the pipe connections between it and the heating device.

Much of the difficulty encountered in domestic hot-water service originates in this unit and, unless the piping arrangement for circulation of the heated water is properly installed, the efficiency of the entire hot-water system is affected.

Construction of the Hot-Water Tank. There are two types of tanks used for the storage of hot water: (1) The small hot-water tank (range boiler); 12) the large hot-water tank (storage tank).

The range boiler generally is constructed of galvanized sheet steel or copper, Fig. 219. It is built into a cylindrical shape having concave ends, and all of the seams are welded or riveted to assure strength. They are made in standard and extra heavy weights and are conveniently tapped for the heater connections. The range boiler varies in size from 12 to 24 inches in diameter and is not more than 6 feet long. It may be used in either a vertical or horizontal position. Fig. 220 illustrates a storage tank which is constructed of heavy gauge sheet metal and generally is coated with a rust-proof paint instead of being galvanized as in the case of the range boiler. These tanks range in size from 24 to 54 inches in diameter and are not more than 15 feet long. They can be tapped for horizontal or vertical installations and are used on larger installations where hot water needs are greater.