A tasteless, transparent, inodorous, liquid, almost incompressible, its absolute diminution being about one twenty-thousandth of its bulk, possesses the liquid form only, at temperatures between thirty-two degrees and two hundred and twelve Fahrenheit. Chemically considered, it is a compound substance of hydrogen and oxygen, two volumes of hydrogen to one volume of oxygen. Water is the most powerful and universal solvent known.

The gallon is the unit of measure for water. The unit of water pressure is the pound per square inch, one gallon of water measures .134 cubic feet and contains 231 cubic inches and weighs about eight and one-third pounds, or sixty-two and one-third pounds per cubic foot,

The above is figured at sixty-two degrees Fahrenheit, which is taken as a standard temperature.

The weight of a column of water of one inch area and twelve inches high, at sixty-two degrees Fahrenheit is .433 pounds, on

.433x144=62.35 pounds per cubic foot.

The pressure of still water, in pounds, per square inch, against the side of any pipe or vessel, of any shape whatever, is equal in all directions, downwards, upwards or sideways. To find the pressure in pounds, per square inch, of a column of water, multiply the height of the column in feet, by .433, approximately one foot of elevation, is equal to one half-pound pressure per square inch.

The head is the vertical distance between the level surface of still water and the height in the pipe, unless caused by pressure such as by a pump, etc. Water pressure is measured in pounds per square inch, above atmospheric pressure, by means of a pressure gauge. To ascertain the height water will rise, at any given pressure, divide the gauge pressure by .433; the result is the height in feet.

Example: The pressure gauge on a supply pipe in a basement shows 25 pounds' pressure. To what height will water rise in the piping throughout the building?

While water will rise to this height, sufficient head should be provided to furnish a surplus head of about ten feet above the highest point of delivery, to insure a respectable velocity of discharge.

It is frequently desired to know what number of pipes of a given size is equal in carrying capacity to one pipe of a larger size. At the same velocity of flow, the volume delivered by two pipes of a different size is proportionate to the square of their diameters, thus: A four-inch pipe will deliver the same volume as four two-inch pipes.

Example:

2 inches X 2 inches = 4 square inches. 4 inches X 4 inches =16 square inches. 16 inches ÷ 4 inches = 4 2-inch pipes.

With the same head, however, the velocity being less in a two-inch pipe, the volume delivered varies about as the square root of the fifth power. Thus one four-inch pipe is actually equal to 5.7 two-inch pipes.

Example: With the same head, how many two-inch pipes will it take to equal one four-inch pipe?

Solution: 25 = 2 X 2 X 2 X 2 X 2 = 32 and the √32 = 5.7 nearly.

In other words, the decrease in loss by friction in the four-inch pipe, in comparison with the two-inch pipes, is equal to 1.7 two-inch pipes over the actual square of their respective areas.

Water boils or takes the form of vapor or steam at 212 degrees Fahrenheit, at a mean pressure of the sea level, or 14.696 pounds per square inch. Water freezes, or assumes a solid form, that of ice, at 32 degrees Fahrenheit, at the ordinary atmospheric pressure, and ice melts at the same temperature. The point of maximum density is reached at 39.2 Fahrenheit, that is, water at that temperature occupies its smallest possible volume. If cooled further, it expands until it solidifies, and if heated, it expands.

Hardness of water is indicated by the easy manner with which it will form a lather with soap, the degree of hardness being based on the presence and amount of lime and magnesia. The more lime and magnesia in a sample of water, the more soap a given volume of water will decompose. The standard soap measurement is the quantity required to precipitate or neutralize one grain of carbonate of lime. It is commonly recommended that one gallon of pure, distilled water takes one soap measure to produce a lather, and, therefore, one is deducted from the total amount of soap measurements found to be necessary to produce a lather in a gallon of water, and in reporting the number of soap measurements or degrees of hardness of the water sample.

The impurities which occur in waters are of two kinds, mechanical and physical, dirt, leaves, insects, etc., are mechanical and can be removed by filtration. It is said that these impurities are held in suspension.

Solutions of minerals, poisons and the like are physical and are designated as those held in solution.

Freshening water to render it palatable is accomplished by aeration, that is, by exposing water to the action of the air, by passing air through it or raising it to an elevation built for that purpose, protected from dust and other impurities of the air, if the water is to be used for drinking purposes, and allowing it to run down an incline, which is slatted or barred, so as to break it up into small particles, and allow it to become saturated with air.

This process, however, is of no practical use for actual purification.