FireOps CalcFriction loss formula
The common coefficient formula used in many pump operator classes is:
Total FL = FL per 100 ft × (hose length ÷ 100)
The C value depends on hose size and hose construction. That is why FireOps Calc should pull hose data from the department setup instead of relying on one generic chart.
Worked example: 2½ inch supply line
Example: 300 ft of 2½" hose flowing 500 GPM with C = 2.
| Step | Math |
|---|---|
| GPM ÷ 100 | 500 ÷ 100 = 5 |
| Square the flow factor | 5² = 25 |
| FL per 100 ft | 2 × 25 = 50 PSI |
| Total hose length | 300 ft = 3 sections of 100 ft |
| Total FL | 50 × 3 = 150 PSI |
What changes friction loss?
Use in training
A good friction loss calculator should not just give an answer. It should show the breakdown so students understand the effect of GPM, hose length, and hose diameter. That is the goal of the FireOps Calc web and mobile app versions.
FAQ
Why does GPM affect friction loss so much?
The coefficient formula squares the flow factor, so increasing GPM can increase friction loss much faster than many new pump operators expect.
Can two supply lines reduce friction loss?
Yes. If two equal supply lines carry the same total flow, each line carries half the flow, which can significantly reduce friction loss.
Should I use exact department hose data?
Yes. Department hose, age, construction, and local training standards may use different coefficients or field values.
Related FireOps Calc pages
Run the calculation in FireOps Calc.
Use the website calculator, install the app, or keep reading the training pages to build stronger pump operator habits.