Reverse Flow
All-in-One Hydraulic Application for the fire service.
Select a saved hose/nozzle setup to quickly fill the calculator.
Select a hydraulic calculation mode.
Reverse Flow Mode: Enter PDP to estimate GPM and Nozzle Pressure based on hose and nozzle characteristics.
Configure supply hose, appliance, and attack line sections.
Used for scenario clarity and displayed in the result. In Reverse Flow mode, nozzle pressure defaults to the highest mathematically reachable value.
Manual PSI value. Defaults to 0.
Rounded Flow
Calculated
—Total FL
—FL / 100'
—Nozzle
—Reaction
—Setup
—Reverse Flow Formula
Total friction loss = PDP − nozzle pressure − appliance/elevation loss.
Friction loss per 100' = total friction loss ÷ hose length in hundreds of feet.
GPM = √(FL per 100' ÷ coefficient) × 100.
Final result rounds to the nearest 5 GPM.
Required PDP Formula
Required PDP = nozzle pressure + friction loss + appliance/elevation loss.
Relay Pumping Formula
Relay PDP = relay friction loss + receiving engine residual + appliance/elevation loss.
Default Coefficients
1.75” = 15.5, 1.88” = 8, 2” = 4, 2.25” = 3, 2.5” = 2, 3” = 0.8, Dual 3” = 0.4, 4” = 0.2, 5” = 0.08
About / How to Use
Reverse Flow Mode Estimates GPM by working backwards using PDP, Nozzle Pressure, and Friction Loss.
Required PDP Mode Calculates the pump discharge pressure needed to achieve a target GPM.
Relay Pumping Mode Calculates the required PDP for a relay pumper to supply a receiving unit with a specific target flow.
For smoothbore calculations, select the tip size manually when in PDP mode. Smoothbore nozzle pressures will be calculated automatically in Reverse Flow mode.
This calculator is intended for training and reference. Always follow local pump charts, equipment testing, department policy, and instructor guidance.