FireOps CalcPDP = FL + NP ± Elevation + Appliance Loss
FL = friction loss
NP = nozzle pressure
Step-by-step process
Start with the nozzle pressureUse the nozzle pressure required by the nozzle or department standard. Common training examples use 50 PSI for many handline smooth bores and 100 PSI or 50 PSI for fog nozzles depending on the nozzle.
Add the hose friction lossCalculate the friction loss for the hose size, length, coefficient, and flow.
Adjust for elevationAdd pressure for uphill or above-grade operations. Subtract pressure for downhill or below-grade operations when appropriate.
Add appliance lossAdd any loss for wyes, manifolds, standpipe appliances, master stream devices, or department-specific appliances.
Set and verifySet the pump pressure, then verify line performance by feedback, flow, nozzle reaction, and department procedures.
Worked example
Nozzle pressure50 PSI
Friction loss106 PSI
Elevation0 PSI
Appliance loss0 PSI
Required PDP156 PSI
Example: a 200 ft 1¾ inch line flowing 185 GPM with C=15.5 has about 106 PSI friction loss. Add a 50 PSI nozzle pressure for a calculated PDP of about 156 PSI.
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
What does PDP mean?
PDP means pump discharge pressure. It is the discharge pressure needed to deliver the desired flow and nozzle pressure after friction loss, elevation, and appliance loss are included.
Should I round pump pressure?
Many departments round to a practical operating pressure. Use your department SOPs and training standards.