How to Convert Water Pressure to Pounds
Water pressure is often measured in "bars" or "atmospheres" in open water. A "bar" equals 100 kilopascals, or 14.5 pounds per square foot. An "atmosphere" represents the pressure exerted by the weight of the Earth's atmosphere at sea level, about 14.7 pounds per square foot. As you go farther underwater, pressures increase at about 1 atmosphere per 33.3 ft. of depth. Converting water pressure to pounds per square foot may be a two-step process where you first calculate the water pressure based on depth, then convert depth to pounds per square foot.
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Instructions
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Use the calculator to divide the depth to an object or simply to a point in the water column by 33 to determine the water pressure in atmospheres. The water column is the part of the ocean or other body of water you're concerned with, from the surface to the bottom.
When Dr. Robert Ballard found the wreck of the RMS Titanic in 1985, the wreck lay on the bottom at a depth of 12,467 feet. Dividing 12,467 by 33 tells you that the water pressure at that depth was 377.7878788 atmospheres.
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Convert the water pressure measured in bars to pounds per square inch by multiplying the number of bars by 14.5, since a bar equals 14.5 pounds per square inch of pressure. If water pressure at depth is given in bars, multiply the number of bars by 14.5 to determine the pressure in pounds per square inch.
The water pressure at the wreck of the RMS Titanic is 382.9987461 bars. Multiplying 382.9987461 by 14.5 shows that the water pressure at that depth is about 5,553.4818182 pounds per square inch.
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Multiply the number of atmospheres by 14.7 to determine the pressure in pounds per square inch: 377.7878788 x 14.7 = 5,553.4818182 pounds per square inch of water pressure at the average depth of the RMS Titanic.
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Tips & Warnings
Since the weight of water is constant throughout the water column, it has no effect on "water pressure" at depth. Water pressure represents only the effect of the weight of the atmosphere on the water column.
Drawing the figures in the calculations out to seven decimal places is necessary for accuracy.
