Hazen-Williams Water Pressure Drop Flow Rates Equations and Calculator

Fluid Power Equipment

Hazen-Williams Water Pressure Drop Flow Rates Equations and Calculator

The Hazen–Williams equation is an empirical relationship which relates the flow of water in a pipe with the physical properties of the pipe and the pressure drop caused by friction. It is used in the design of water pipe systems such as fire sprinkler systems , water supply networks , and irrigation systems. It is named after Allen Hazen and Gardner Stewart Williams.

The Hazen–Williams equation has the advantage that the coefficient C is not a function of the Reynolds number , but it has the disadvantage that it is only valid for water . Also, it does not account for the temperature or viscosity of the water.

 Hazen Williams Coefficient, C = Pressure drop over pipe length, DP = psi Editable Variable Colored Yellow Pipe Water Flow Rate in GPM Length Pipe Diameter in Inches ft Hazen Williams Equation as used in this Calculator: Q = 0.442 C D2.63(DP/L)0.54 Where: Q is the water flow rate in gpm D is the pipe diameter in inches L is the pipe length in ft DP is the pressure difference across pipe length L in psi