Behind every reliable fire protection system lies a simple yet powerful equation.
If you’re working in the field of fire protection, you’ve likely used — directly or indirectly — the Hazen-Williams Equation. This formula, developed more than a century ago, remains a cornerstone in the design of water-based fire protection systems.
But who were Hazen and Williams, and why does their equation still matter today?
Meet the Men Behind the Equation
Allen Hazen (1869–1930) was a civil engineer known for his work in water treatment and distribution systems in the United States. He was a pioneer in sanitary engineering and contributed significantly to modern water quality standards.
Gardner Stewart Williams (1866–1950) was a professor of civil engineering who specialized in hydraulics and pipe flow. His expertise complemented Hazen’s, and together they developed what is now known as the Hazen-Williams Equation — an empirical formula to estimate friction loss in water flow through pipes.
Why It Matters in Fire Protection Design
In fire protection engineering, accurate and fast calculations are essential. The system must deliver water at the right pressure and flow rate, instantly and reliably, during emergencies. The Hazen-Williams Equation is ideal for this purpose because:
- It’s specifically designed for water flow — the primary medium in most fire protection systems.
- It’s simple and efficient, not requiring complex variables like fluid viscosity or Reynolds number.
- It supports quick pipe sizing and head loss estimation, which speeds up the design process.
Fire sprinkler systems, hydrant networks, and standpipe installations often rely on Hazen-Williams-based calculations to ensure compliance with NFPA and local fire codes.
Still Relevant After 100+ Years
Despite being developed in the early 1900s, the Hazen-Williams Equation remains a trusted tool for fire protection system design worldwide. While other methods like Darcy-Weisbach offer more precision for diverse fluids, Hazen-Williams is preferred for its speed and simplicity — especially when dealing with clean water in standardized pipe materials.
Thank You, Hazen and Williams
Whether you’re optimizing a sprinkler layout, verifying hydraulic calculations, or modeling a fire pump curve — you’re benefiting from the legacy of Hazen and Williams.
Their contribution has made modern fire protection more efficient, reliable, and accessible.
So the next time you open a calculation sheet or hydraulic modeling software, remember: your job is just a little easier, thanks to two brilliant minds from over a century ago.