Hazen-Williams friction loss equation is valid for water at temperatures typical of city water supply systems (40 to 75 oF; 4 to 25 oC).
To: LMNO Engineering home page
Design of Circular Water Pipes Calculator Table of Hazen-Williams Coefficients (C) Unit Conversions
k is a unit conversion factor:
k=1.318 for English units (feet and seconds). k=0.85 for SI units (meters and seconds)
Rh=hydraulic radius=D/4 for circular pipe
The Hazen-Williams method is only valid for water flowing at ordinary temperatures (about 40 to 75 oF). For other liquids or gases, the Darcy-Weisbach method should be used. Major loss (hf) is the energy (or head) loss (expressed in length units - think of it as energy per unit weight of fluid) due to friction between the moving fluid and the duct. It is also known as friction loss. The Darcy-Weisbach method is generally considered more accurate than the Hazen-Williams method. However, the Hazen-Williams method is very popular, especially among civil engineers, since its friction coefficient (C) is not a function of velocity or duct diameter. Hazen-Williams is simpler than Darcy-Weisbach for calculations where you are solving for flowrate, velocity, or diameter. More Discussion and References.
© 1998-2001 LMNO Engineering, Research, and Software, Ltd. (All Rights Reserved)
LMNO Engineering, Research, and Software, Ltd.
7860 Angel Ridge Rd. Athens, Ohio USA (740) 592-1890