FireOps CalcPDP = FL + NP ± Elevation + Appliance Loss
FL per 100 ft = C × (GPM ÷ 100)²
Step-by-step process
Pick the target flowUse the nozzle or department target GPM.
Enter the hose lengthInclude the full charged length between the pump and nozzle.
Use the correct hose coefficientMany training examples use a low C-value for 2½ inch hose, but use your department data if available.
Add nozzle pressureSmooth bore, low-pressure fog, and high-pressure fog nozzles may all require different nozzle pressures.
Review nozzle reaction and staffingHigh-flow handlines require appropriate staffing and control.
Worked example
Line250 ft of 2½ inch
Flow265 GPM
C-value2
Nozzle pressure50 PSI
Calculated PDPabout 85 PSI
This example uses C=2 and a 50 PSI nozzle pressure. Your result may differ if your nozzle requires 100 PSI or your hose coefficient is different.
Common mistakes to avoid
- Using a default nozzle pressure that does not match the actual nozzle.
- Forgetting extra hose, elevation, or appliance loss.
- Using textbook coefficients when your department has known hose data.
- Treating a training estimate as a replacement for department SOPs or instructor direction.
How FireOps Calc helps
FireOps Calc is built to make this process faster on a phone. Open the web calculator, enter your hose, nozzle, flow, elevation, and appliance values, then review the math breakdown instead of only seeing a final number.
FAQ
Why is 2½ inch friction loss lower than 1¾ inch?
The larger diameter reduces resistance to flow, so it can move more water with less pressure loss.
Should 2½ lines always be pumped lower?
Not always. The required nozzle pressure, appliance loss, elevation, and flow target still determine the final PDP.