Errata.The Building Principles column on this topic in the September/October issue on page 58, reflected an error in calculations. The calculations should read as follows: The first and simplest method of supplying pressure is gravity Gravity The gravitational attraction at the surface of a planet or other celestial body. The quantity g is often referred to simply as “gravity’’ or “the force of gravity’’ of Earth, both of which are incorrect. The well pump moves the water from underground to a storage tank whose height has been set to deliver a regular, reliable system pressure. For each 1 pound of pressure required, the water needs to be raised about 2.31'. Put another way raising the water I 'increases the pressure 0.43 pounds per square inch Noun 1. pounds per square inch - a unit of pressure psi pressure unit - a unit measuring force per unit area (psi PSI - Portable Scheme Interpreter ). Average system pressure range at a faucet or showerhead should be between 30 and 50 psi. This means that the lowest water level above the highest faucet has to be at least 30 psi * 2.31 = 69.3' above the highest faucet. The upper end of the operating range is calculated the same way: 50 * 2.31 = 115.5' above the highest faucet. Another way of looking at this is that the fluctuating fluc·tu·ate v. fluc·tu·at·ed, fluc·tu·at·ing, fluc·tu·ates v.intr. 1. To vary irregularly. See Synonyms at swing. 2. To rise and fall in or as if in waves; undulate. v. height of the water in the tank ("operating range") is about 115.5' - 69.3' = 46.2'. At the bottom of that same page the cent ([cents]) symbol was inadvertently used when the word "diameter diameter - The diameter of a graph is the maximum value of the minimum distance between any two nodes. " should have been indicated. |
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