fluidwt 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 IN2 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.

It drives me nuts to see Engineers calculate hydrostatic pressure to the nth degree….  the density of water changes dramatically with temperature, and temperature increases with depth.water_density

as you can see… 8.3 is fine.

8.3 x .052 x 10,500′ = 4532 Psi