WATER SUPPLY · INDEPENDENT SYSTEMS
Wildfire Sprinkler Water Runtime Calculator
Calculate how long stored water can support sprinklers or hose lines, account for refill flow and reserve volume, and work backwards from a target runtime to required tank capacity.
CALCULATED RUNTIME
56% of target runtime
The selected storage and refill cannot sustain demand for 2 hours.
TRANSPARENT FLOW BALANCE
Every gallon has a job.
The calculator separates physical tank volume, unusable volume, protected reserve, outlet demand and continuous refill. It assumes all selected outlets run continuously at their entered flow.
Available = Tank × usable fraction − reserveDemand = outlets × flow + other drawRuntime = available ÷ (demand − refill)Verify volume
Use actual stored volume, not nominal tank capacity when partially filled.
Measure flow
Nozzle flow depends on pressure; manufacturer ratings require their stated conditions.
Protect reserve
Keep inaccessible sediment volume and any operational reserve out of the runtime budget.
Test the system
Confirm simultaneous flow, pump duty, suction, filtration and power under controlled conditions.
THE HYDRAULIC CHAIN
A large tank does not guarantee useful flow.
This page balances volume and flow only. Pump curve, elevation head, pipe diameter, friction loss, nozzle pressure, clogged filters and power availability can prevent the assumed flow from reaching the outlets.
Check separately
- Pump flow at required total dynamic head
- Pipe and hose friction loss
- Nozzle operating pressure and pattern
- Generator or battery runtime
- Dry-run and overheat protection
- Local restrictions and fire-service access
Sources and limitations
This is a deterministic storage balance, not an endorsement of exterior sprinkler operation during an incident. CAL FIRE advises residents not to leave sprinklers or water running before evacuation because doing so can reduce critical water pressure. Independent supplementary sources require appropriate professional design and testing.
CAL FIRE: Go Evacuation Guide · CAL FIRE: Hardening Your Home · USDA Forest Service: protecting residences
Quick answers
What happens when refill exceeds demand?
The calculated stored-water runtime becomes indefinite while that refill continues. Tank overflow, source depletion and equipment limits are not modelled.
Is pump flow the same as nozzle flow?
Not necessarily. Available flow changes with pressure, elevation and friction losses.
Should community hydrant or tap flow be assumed?
No. Availability and pressure may fall during an incident; follow local authority instructions.