fluid_{wt} x .052 x Depth = Hydrostatic Pressure

8.34 x .052 x 10,500′ = 4553.64 Psi

So where did this .052 thing come from…

Consider a cube that is 1′ square… If you take the weight of a cubic foot filled with an imaginary liquid that weighs one pound per gallon, it would be… (there are 231 IN^{2} in a gallon)

(12′ x 12′ x 12′)/231 = 7.48051948 lbs.

so now think of just a one inch square at the bottom of that cube – divide by 144 [ 12 x 12 ]

7.48051948 / 144 = .0519480519 …it’s **.052**

Because we used an imaginary fluid that had a value of 1, we can just multiply by our real fluid weight to get the actual hydrostatic force exerted by a 1 inch by 1 inch by 12 inch column.

Hydrostatic pressure is the same if you measure it at the bottom of a bunch of straws that you hook together or if you measure it at the bottom of a lake; the fluid exerts the same amount of force per square inch… the only factor that matters is the TVD (True Vertical Depth) of the fluid column.

{SIDE NOTE}

It drives me nuts to see Engineers calculate hydrostatic pressure to the n^{th} degree…. the density of water changes dramatically with temperature, and temperature increases with depth.

as you can see… 8.3 is fine.

8.3 x .052 x 10,500′ = 4532 Psi

{END OF SIDE NOTE}