You may use this on-ilne hydraulic calculation tool to make quick and basic estimates of pressure drop by friction loss in pipes. This can be useful to estimate Fire hydrant expected flow given the pipe diameter, the available pressure and the roughness constant C (C - relates to the pipe material and age) If you need accurate results, you should use a more complex and certified software. Our tool allows you to choose metric or US units and is using this Hazen-Williams formula: