What is friction loss per 100 ft and how is it used in calculations?

• A. It is a chart value representing pressure loss for 100 ft of hose at a given GPM; multiply by total length in hundreds of feet to estimate total FL.
• B. It represents the velocity of the water.
• C. It is used to determine hose diameter only.
• D. It is a fixed value independent of GPM.

Answer: (A)

Friction loss per 100 ft is the pressure drop caused by fluid friction as water flows through hose, expressed as a psi value for each 100 feet of hose at a specific flow rate (GPM) and hose size. This value comes from friction loss charts that relate GPM and hose diameter to how much pressure is lost per 100 ft.

To use it in calculations, take the friction loss per 100 ft for your hose and flow, then multiply by the total hose length expressed in hundreds of feet to obtain the total friction loss along the entire run. For example, if the chart shows 12 psi per 100 ft at the chosen GPM, and you have 200 ft of hose, the total friction loss is 12 psi × 2 = 24 psi. This total is then combined with other pressure considerations to ensure the pump can deliver the required nozzle pressure.

It isn’t a velocity, it isn’t used only to determine hose diameter, and it isn’t a fixed value—it varies with GPM and hose size.