Formula for Pressure in Depths of Liquid


Finding pressure in depths of water

In the operation of pressurized systems you will be primarily concerned with the pressures exerted by water. Water pressures are directly related to both the height (depth) and density of water. Pressure is defined as the amount of force acting (pushing) on a unit area.

Consider a cubic meter of water to have a mass of 1000 kg and, the force acting downward to be 1000 x 9.8 or 9800 Newton. As this force is acting on 1.0 M2 the pressure on the base of the cube will be 9800 N or 9.8 Kpa per 1.0 m2.

It follows that at a depth of 2.0 m the pressure will be 2 x 9.8 or 19.6 Kpa and 3.0 m it will be 3 x 9.8 or 29.4 Kpa. Therefore, to find the pressure in water simply multiplies 9.8 by the depth in meters. Remember that the result of this calculation will give you kilopascals.

Formula

Pressure (P) = 9.8 x depth (m) = Kpa

P = 9.8 x depth (m) x SG = Kpa (If working with substances other than water their specific gravity(SG) must be factored in)

Example:

Find the pressure in water at a depth of 150m.

P = 9.8 x 150

P= 1470 Kpa

Example 2:

If a pressure gauge on a non pressurized tank reads 24.3 Kpa, how many meters of water are there in the tank?

Depth= 24.3 / 9.8

depth= 2.48 m