Friction Loss Calculator

Fluid friction against internal pipe walls creates resistance, leading to a loss of pressure and head. This calculator relies on the Hazen-Williams empirical formula, which is widely used for water supply and distribution systems. The primary equation determines head loss in meters: Headloss = 10.67 * Length * ((Flowrate / Coeff)^1.852) / (Dia^4.8704), where Length is measured in meters, Flowrate is in cubic meters per hour, Coeff is the Hazen-Williams roughness coefficient, and Dia is the inner diameter in meters. Once the head loss is established, the pressure loss (PL) in Pascals is calculated by multiplying the head loss by the specific weight of water and gravity conversion constant: PL = Headloss * 9810.

Imagine you are designing a municipal water line. You have a smooth PVC pipe with a Hazen-Williams roughness coefficient (Coeff) of 150, an inner diameter (Dia) of 0.1 meters, and a total length of 100 meters. The water flow rate (Flowrate) is set at 20 cubic meters per hour. First, divide the flow rate by the roughness coefficient: 20 / 150 = 0.1333. Raise this result to the power of 1.852, yielding approximately 0.0245. Next, raise the pipe diameter (0.1) to the power of 4.8704, yielding approximately 0.00001348. Divide 0.0245 by 0.00001348, which gives 1817.49. Multiply this by the length (100) and the constant 10.67, resulting in a head loss of roughly 1,939.2 meters. Finally, multiply the head loss by 9810 to find the pressure drop, resulting in approximately 19,013,592 Pascals (or 19.01 MPa).

Always ensure your input units are consistent; converting millimeters to meters before performing calculations prevents massive sizing errors. Keep in mind that older pipes accumulate scale and sediment, which lowers the Hazen-Williams coefficient and drastically increases friction loss over time. When designing closed-loop systems, account for minor losses from valves, elbows, and fittings alongside major friction losses calculated here to maintain accurate system performance.