FireOps CalcUsable shuttle GPM = Usable gallons ÷ Cycle time in minutes
Total shuttle GPM = GPM per tender × Number of tenders
Step-by-step process
Find usable tank volumeUse the practical gallons available after accounting for reserve, incomplete dumps, or local practice.
Time the full cycleInclude fill time, travel to the scene, dump time, and return travel.
Calculate one tender flowDivide usable gallons by cycle time.
Multiply by tendersMultiply by the number of tenders operating in the shuttle.
Compare to fire flow needIf demand is higher than shuttle supply, the operation needs more water, shorter cycles, or reduced flow demand.
Worked example
Tank size2500 gal
Usable amount2250 gal
Cycle time10 min
One tender flow225 GPM
Two tenders450 GPM
The weakest part of the shuttle often becomes fill site speed, dump site layout, or travel time—not the tank size alone.
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 not use full tank size?
Real shuttles may not deliver every gallon every cycle. Usable gallons are often more realistic for planning.
Can this replace ISO or department water supply planning?
No. It is a quick training and estimating tool. Use department procedures and formal water supply planning where required.