According to the Hazen-Williams formula, what is the needed coefficient for 1 1/4 inch pipe?

The Hazen-Williams formula is commonly used to calculate the friction loss in water flowing through pipes, specifically in the context of fire protection and plumbing systems. The formula incorporates a coefficient known as the Hazen-Williams coefficient, which varies based on the material and size of the pipe.

For a 1 1/4 inch pipe, the appropriate Hazen-Williams coefficient is 120. This specific coefficient is derived from empirical data reflecting the hydraulic characteristics of different pipe materials and sizes. A coefficient of 120 suggests that the pipe material has reasonably good flow characteristics—neither too rough (which would lead to greater friction losses) nor too smooth (which could imply less turbulence and lower flow rates).

Using the correct coefficient is critical in design calculations, as it impacts how pressure losses are estimated, ultimately affecting the sizing of pumps, pipe diameter, and overall system efficiency. Thus, knowing that the coefficient for a 1 1/4 inch pipe is 120 is essential for accurate design and assessment in water-based systems.