2025-02-14 00:00:00 Fire Hydraulics is offered as a free app with no ads and no in-app purchases. Usage of this app and results are for academic purposes only. Do not rely on the results for actual fire incidents. Fire Hydraulics uses the Pump Discharge Pressure formula alternatively known as the Engine Pressure formula to display Engine Pressure, Nozzle Pressure, Friction Loss, Appliance Loss, and Elevation Loss/Gain.