Hazen-Williams Water Pressure Drop Flow Rates Equations and Calculator

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Hydraulic and Pneumatic Knowledge

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

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