The Golden State: Where & How to Live, Secure, Visit, Enjoy and Thrive in California
How To Design And Install Plumbing
Surrounding the earth's surface is a volume of a mixture of gases, often referred to as a blanket, or ocean, of atmosphere. It contains approximately 21 per cent of oxygen, 78 per cent nitrogen, .94 per cent argon, .003 per cent carbon dioxide, as well as neon krypton, ozone and other gases of lesser importance. Scientific data ' establish the atmosphere as having a depth of about 300 miles. The 50 miles of air closest to the earth's surface apparently have direct influence on the problems affecting ventilation, and, therefore, this depth of atmosphere is of chief concern to the plumber. The atmosphere has a density of about 1.29 grams per liter (1000 c.c.) under S.T.P. (Standard Temperature and Pressure) conditions; and a column of atmosphere 1 inch square and about 50 miles in length exerts a pressure on the earth's surface of 14.72 pounds. The conclusion derived from these scientific facts is that every inch of the earth's surface, or all objects on it, be they liquid, solid, or gas in form, are under pressure of 14.72 pounds per square inch. Scientists have established sea level as the basis of this pressure. Any level above or under the level of the sea would be subjected to lesser or greater pressure.
One of the common properties of the gases which compose the atmosphere is compressibility. Air can be compressed and, in this condition, develops pressure greater than atmospheric. This fact can be proved by the automobile tire under pressure, to name an object with which everyone is familiar. Air also can be withdrawn from a space or container, and this condition is termed a vacuum or partial vacuum, depending on the volume of air removed. A partial vacuum, therefore, would indicate a pressure less than that of one atmosphere.
The power of some of the gases to combine with other elements to form chemical compounds is also of importance, because these compounds may be of an acid nature and thus affect the piping material of the plumbing system. This phase of investigation, however, is still in the experimental stages and not much has been done with it at this time.
In the discussion of trap seal loss and retarded flow, a pressure of less than one atmosphere (14.72 pounds) will be referred to as a minus pressure. A pressure greater than one atmosphere will be called a plus pressure.
