Calculating Pressure within a Fluid Column

It is important to remember when measuring pressure within a liquid that the pressure is related not to the volume of the liquid, but to the height of the fluid column above the test point. This can be referred to as ‘hydrostatic pressure’ (for more on this term and related mathematical formulas, click here to visit Wikipedia). In other words, the pressure measured at 1 foot below the surface of an Olympic swimming pool should be the same as the pressure measured at 1 foot below the surface of a bath tub or 1 foot below the surface of a bucket. The units of measure typically used for hydrostatic pressure are inches of water column (WC) or feet of WC (also fluid column).


In the case of water, we can consider the following:

27.679 inches of WC is the approximate equivalent of 1 PSI at 40°C.
Water density at 60°F (15.6°C) = 62.37 pounds per cubic foot.
The pressure exerted by a column of water one foot in height is:
pounds x square foot = .4331 pounds


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