Hazen-Williams Formula:

Best suited for: Water flow in fire protection systems like sprinkler systems, standpipes,
and fire hydrants.

Why it's preferred:
o
Simpler to use and doesn't require calculation of Reynolds number or friction
factor.
o
Common in fire protection codes and standards (e.g., NFPA 13, NFPA 14).
o
Works well for turbulent flow of water in pipes typically used in firefighting
systems.
Darcy-Weisbach Formula:

Best suited for: General fluid dynamics, including gases and more precise water flow
applications.

Why it's not typically used in firefighting:
o
Requires calculating or looking up the friction factor (f) based on Reynolds
number and relative roughness — more complex.
o
While it's more universally accurate (especially for different fluids), it's overkill
for fire system design where simplicity and speed are important.
o
Not commonly found in NFPA guidance.