Pressure Drop in Hose
As liquid is forced through a hose pressure is lost due to the friction between the liquid and the inside wall of the hose. When a large amount of flow (gallons per minute) is forced through a small hose, the velocity (speed) the liquid must travel through the hose is increased and the friction is also increased causing a great amount of pressure drop. The liquid carrying capacity of hose Is determined by it s cross section or area rather than it s diameter. Increasing hose size by 2 times increases its area by 4 times.
The chart illustrates the pressure losses that occurs per foot of hose at various flow rates. For example: at a flow of 10 gpm and 1/2 hose, the horizontal 10 gpm line crosses the slanted 1/2 hose line at the 1 psi vertical line. A 25 ft. length of hose would have a 25 psi (1 x 25) loss.