Garden Hose Flow Rate and Time
The amount of water flow from a garden hose. This assumes a free-flowing hose end (not connected to a sprinkler or something). The minutes to supply a given volume is also determined below. Learn more about the units used on this page.
Water Flow Rate
The Equations
This flow calculator uses the Hazen Williams equation to solve for flow assuming that the pressure at the outlet is zero (open to atmosphere) and thus the entire pressure at the hose bib is dissipated by friction losses in the hose. The pressure at the hose bib is assumed to be the dynamic pressure (while water is flowing) not the static pressure (no water flowing). The dynamic pressure will always be less than static pressure and is due to friction losses in the piping leading to the hose bib. Static pressures in most homes is usually 35-80 psi. A reasonable assumption is that dynamic pressures might be 5-10 psi less than that. The dynamic pressure at the hose bib also drops with increased flow rates (additional pressure losses in the piping leading to the hose bib at higher flow rates) and don't stay constant as this calculator assumes. Because of all of these things, this calculator will likely over-estimate flow rates and it is more accurate to simply measure your flow rate using a known volume and a stop watch than to use this calculator. The assumed C factor (internal to the equation constant) is 135 for flexible garden hoses.
Water Flow Rate
Where:
= Water flow rate from the end of the hose (gpm)
= Pressure at the hose bib while hose end is free flowing (dynamic pressure, not static pressure) (psi).
= Hose internal diameter (in)
= The hose length (ft)
Water Flow Time
Where:
= Time it will take to fill the specified volume (min)
= Volume needed (gal)
= Flow rate from the garden hose (gpm)