How to figure gallonage of cylindrical tank

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How to figure gallonage of cylindrical tank

Postby LucyLu » Tue Jun 19, 2007 4:45 am

Need to find out what the gallonage is on my well tank. It measures 3 feet 1 1/2 " long and has a diameter of 1 foot 4". The circumference measures 4 feet 4". Thanks a lot.
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Joined: Tue Jun 19, 2007 4:26 am

Postby Dirtman » Wed Jun 20, 2007 10:09 am

The formula for calculating the volume of a cylinder in gallons (with perpendicular ends) using inches is: PI*R^2*L/231

PI = 3.1415927
R = radius in inches
L = length in inches
231 = cubic inches in a US gallon


3.1415927 * 8 * 8 * 37.5 / 231 = 32.64 gallons

However, most pressure tanks have semi-elliptical tank ends plus an expandable bladder, which allows the tank to hold pressure when a pump isn't on. The above formula does not account for the semi-elliptical tank ends or a pressure bladder.
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