Pressure Head

The Pressure Head calculator computes the pressure based on Gravity-Fed Water from a Tank.

INSTRUCTIONS: Choose units and enter the following:

• (h)  Height of Reservoir or Rank above current position.
• (ρ) Density of Fluid (e.g. water 1000 kg/m³)

Fluid Pressure (WP): The pressure is returned in pounds per square inch (PSI).  However, this can be automatically converted to compatible units via the pull-down menu.

The Math and Science

The calculator computes the water pressure (p) that can be realized below a tank based on the height of storage.  The pressure is returned in pounds force per square inch (lbs/in²) which is equivalent to pounds per square inch (PSI). The pressure from an elevated tank of water due only on the flow caused by gravity can be calculated based on the Pressure Head equation.  It is mathematically expressed as:

    `h = p/gamma = p/ (rho * g)`

where

• h = pressure head (Length, typically in units of m);
• p = fluid pressure (force per unit area, often as Pa units); and
• `gamma` is the specific weight (force per unit volume, typically N/m³ units)
• ρ = density of the fluid (mass per unit volume, typically kg/m³)
• g = acceleration due to gravity (rate of change of velocity, given in m/s²) 

In this equation, `rho` is 1,000 kg/m³ for the mean density of fresh water, and `g` is 9.8 m/s².  

 Solving for `p` (fluid pressure):

    `p = psi * rho * g`     or applying the constants and units   `p = psi_m * 1000_("kg/"m^3) * 9.8_("m/"s^2)`

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