Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications!

Hazen-Williams Equation - calculating Head Loss in Water Pipes

Friction head loss (ftH2O per 100 ft pipe) in water pipes can be estimated with the empirical Hazen-Williams equation

Sponsored Links

The Darcy-Weisbach equation with the Moody diagram is considered to be the most accurate model for estimating frictional head loss for a steady pipe flow. Since the Darcy-Weisbach equation requires iterative calculation an alternative empirical head loss calculation like the Hazen-Williams equation may be preferred:

h = 0.2083 (100 / c)1.852 q1.852 / dh4.8655                          (1)

where

h = friction head loss in feet of water per 100 feet of pipe (fth20/100 ft pipe)

c = Hazen-Williams roughness constant

q = volume flow (gal/min)

dh = inside hydraulic diameter (inches)

Note that the Hazen-Williams formula is empirical and lacks a theoretical basis. Be aware that the roughness constants are based on "normal" conditions with approximately 1 m/s (3 ft/sec).

teh Related Mobile Apps from The Engineering ToolBox Engineering Toolbox Apps

- free apps for offline use on mobile devices.

Online Hazens-Williams Calculator

Imperial Units

The calculators below can used to calculate the specific head loss (head loss per 100 ft (m) pipe) and the actual head loss for the actual length of pipe:

l - pipe or tube length (ft)

c - design coefficient determined for the type of pipe or tube

q - flow rate (gal/min)

dh - inside hydraulic diameter (inch)

SI Units

l - pipe or tube length (m)

cdesign coefficient determined for the type of pipe or tube

q - flow rate (liter/sec)

dh - inside hydraulic diameter (mm)

The Hazen-Williams equation is not the only empirical formula available. Manning's formula is commonly used to calculate gravity driven flows in open channels.

The flow velocity can be calculated as

v = 0.408709 q / dh2                                (2)

where

v = flow velocity (ft/s)

Limitations

The Hazen-Williams equation is assumed to be relatively accurate for water flow in piping systems when

For hotter water with lower kinematic viscosity (example 0.55 cSt at 130 oF (54.4 oC)) the error will be significant.

Since the Hazen-Williams method is only valid for water flow - the Darcy Weisbach method should be used for other liquids or gases.

  • 1 ft (foot) = 0.3048 m
  • 1 in (inch) = 25.4 mm
  • 1 gal (US)/min =6.30888x10-5 m3/s = 0.227 m3/h = 0.0631 dm3(liter)/s = 2.228x10-3 ft3/s = 0.1337 ft3/min = 0.8327 Imperial gal (UK)/min
Sponsored Links

Related Topics

Related Documents

Tag Search

  • en: hazen-williams equation
Sponsored Links

Search the Engineering ToolBox

Engineering ToolBox - SketchUp Extension - Online 3D modeling!

3D Engineering ToolBox Extension to SketchUp - add parametric components to your SketchUp model

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro .Add the Engineering ToolBox extension to your SketchUp from the SketchUp Pro Sketchup Extension Warehouse!

Translate this page to
About the Engineering ToolBox!

Citation

This page can be cited as

  • Engineering ToolBox, (2004). Hazen-Williams Equation - calculating Head Loss in Water Pipes. [online] Available at: https://www.engineeringtoolbox.com/hazen-williams-water-d_797.html [Accessed Day Mo. Year].

Modify access date.

Customize Ads in the ToolBox

Make ads more useful in Google Ad Settings .

. .

close

3D Engineering ToolBox - draw and model technical applications! 2D Engineering ToolBox - create and share online diagram drawing templates! Engineering ToolBox Apps - mobile online and offline engineering applications!

Scientific Online Calculator

Scientific Calculator

9 21

Sponsored Links
.