Save, load, and manage operational hose/nozzle setups.
Select a hydraulic calculation mode.
Reverse Flow Mode: Enter PDP to estimate GPM and Nozzle Pressure based on hose and nozzle characteristics.
Build the supply-side hydraulic path feeding the attack lines.
Dual supply assumes two matching supply lines feeding a Siamese connection.
Pump to first appliance.
Second hose section between appliances.
Configure nozzle paths and attack line hydraulics.
Optional single supply section before the attack line.
Configure the supply hose feeding the attack section.
Select a nozzle style to show only the inputs required by that hydraulic model.
Used for scenario clarity and displayed in the result. In Reverse Flow mode, nozzle pressure defaults to the highest mathematically reachable value.
Default is 25 psi. Change only if your device has been flow tested.
Elevation above the pump discharge.
Manual PSI value. Use negative values for elevation gain/downhill pumping.
Splits total flow evenly across two identical supply lines for friction loss calculation.
Split Lay PDP
— PSISupply Layout
—Total Supply Flow
—Supply Friction Loss
—Appliance Loss
—Section Flow
—Supply 2 FL
—Appliance 2 Loss
—Delivered Flow
—Nozzle Pressure
—Attack Line FL
—Nozzle Reaction
—Delivered Flow
—Nozzle Pressure
—Attack Line FL
—Nozzle Reaction
—Standpipe Ops PDP
— PSITotal Flow
—Supply Line FL
—Standpipe Loss
—Driving Line
—Flow
—Friction Loss
—Elevation Loss
—Nozzle Pressure
—Nozzle Reaction
—Flow
—Friction Loss
—Elevation Loss
—Nozzle Pressure
—Nozzle Reaction
—Rounded Flow
Calculated
—Total FL
—FL / 100'
—Nozzle
—Reaction
—Setup
—Turbo Loss
—Flow and reaction shown for solid-stream operation.
Formula / Hydraulic Reference
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.
Wye Ops Formula
Wye Ops PDP = supply friction loss + gated wye appliance loss + highest attack-line pressure demand.
Attack demand = nozzle pressure + attack hose friction loss.
When one line closes, the original PDP remains fixed and the remaining line is recalculated from the available pressure.
Smoothbore flow = 29.7 × tip diameter² × √nozzle pressure.
Split Lay Formula
Total PDP = supply friction loss + appliance loss + highest attack-side pressure demand.
For unequal attack lines, the higher-demand line drives PDP. Lower-demand lines are recalculated to show actual delivered nozzle pressure, flow, friction loss, and nozzle reaction.
Automatic Fog actual flow = target flow × √(actual nozzle pressure ÷ target nozzle pressure). Fixed Fog actual flow = rated flow × √(actual nozzle pressure ÷ rated pressure).
Smoothbore flow = 29.7 × tip diameter² × √nozzle pressure.
Standpipe Ops Formula
Required PDP = highest-demand attack line + standpipe loss + supply friction loss.
Line requirement = nozzle pressure + attack hose friction loss + elevation loss.
Supply FL = C × (supply flow ÷ 100)² × (supply length ÷ 100).
Elevation is estimated at 5 PSI per floor above Floor 1. Floor 1 is treated as the FDC/pump reference level.
Default standpipe loss allowance is 25 PSI.
When dual matching supply lines are selected, total standpipe flow is divided evenly between both supply lines.
Standpipe outlet pressure is estimated and should be confirmed with an inline gauge whenever possible.
Default Coefficients
1" = 100, 1.5" = 24, 1.75” = 15.5, 1.88” = 8, 2” = 6, 2.25” = 3.5, 2.5” = 2, 3” = 0.8, Dual 3” = 0.2, 4” = 0.2, 5” = 0.08
About / How to Use
What is Reverse Flow?
Reverse Flow is a community project built by firefighters, with firefighters, for firefighters.
This app is one outcome of that project, bringing together operational hydraulic calculators, department reference tools, pump chart management, and training resources shaped through firefighter feedback.
Calculator Modes
Wye Ops Mode
Models a gated wye operation with two attack lines and recalculates remaining-line flow when one line closes.
Required PDP Mode
Calculates the pump discharge pressure required to achieve a desired flow.
Reverse Flow Mode
Estimates achievable flow by working backward from available pump discharge pressure and hydraulic losses.
Split Lay Mode
Models split-supply and split-attack hose layouts, including appliance losses, multiple attack lines, delivered flow, and pressure balancing.
Standpipe Ops Mode
Estimates engine pressure for standpipe stretches using attack demand, elevation, standpipe loss, and FDC supply loss.
Relay Pumping Mode
Calculates relay pumper discharge pressure needed to supply a receiving engine while maintaining residual pressure.
Apparatus Mounted Mode
Supports apparatus-mounted and master stream hydraulic calculations, including elevation and appliance losses.
Pump Charts
Pump Charts allow departments and individual users to save, manage, update, and export commonly used operational hose and nozzle configurations.
Tools
The Tools workspace includes Field Calculators, Equipment Defaults, Equipment Visibility, My Hose Profiles, and other interactive hydraulic utilities.
Field Calculators cover quick utilities such as Smoothbore Flow, Nozzle Reaction, Tank Time, Water Velocity, Hose Coefficient, Friction Loss / 100', and reference charts.
Resources
Resources includes free reference, training, and educational content such as the Training Directory.
Resource material is intended for informational purposes and may vary by manufacturer, department testing, and local policy.
Settings
Equipment Defaults set preferred hose coefficients and selections, Equipment Visibility hides unused equipment from dropdowns, and Appearance lets you follow system theme or force light or dark mode.
Disclaimer
Reverse Flow is intended for training, planning, reference, and operational decision support.
Actual pump discharge pressure requirements may vary based on apparatus plumbing, valves, appliances, intake conditions, hose characteristics, equipment testing, and local operating procedures.
Always follow department policy, manufacturer guidance, verified pump charts, and instructor direction.