Water Tank Refill Time Calculator
Estimate time to fill the remaining tank capacity under a stated flow rate. The tool shows the method and key assumptions so you can inspect how the input values lead to the estimate.
How to use this calculator
- Enter tank capacity (litres) using the unit and definition shown beside the input.
- Enter current water volume (litres) using the unit and definition shown beside the input.
- Enter inlet flow rate (litres/minute) using the unit and definition shown beside the input.
- Check that all values refer to the same time period and scenario.
- Review the outputs alongside the assumptions before using them in a decision.
Formula and assumptions
Refill time=(capacity−current volume)/inlet flow rate.
- Assumes constant usable inflow and ignores changing pressure, float valves, interruptions, leakage and dead volume. Use the measured flow at the actual connection.
- The estimate is calculated from values you enter. It does not connect to external accounts, obtain live prices, or validate local regulations or engineering specifications.
Worked examples
Worked example
A 1,500 L tank at 420 L with 18 L/min inlet flow needs about 60 minutes to fill.
Enter total capacity, current volume and measured inlet flow.
Compare the estimate with real fill behaviour and available supply.
Understanding the result
Assumes constant usable inflow and ignores changing pressure, float valves, interruptions, leakage and dead volume. Use the measured flow at the actual connection.
Change one input at a time to see how sensitive the output is to that assumption.
Important notes
Assumes constant usable inflow and ignores changing pressure, float valves, interruptions, leakage and dead volume. Use the measured flow at the actual connection.
Frequently asked questions
What formula does the Water Tank Refill Time Calculator use?
Refill time=(capacity−current volume)/inlet flow rate.
What should I verify before relying on the result?
Assumes constant usable inflow and ignores changing pressure, float valves, interruptions, leakage and dead volume. Use the measured flow at the actual connection.
Can I compare different scenarios?
Yes. Change one assumption at a time, keep units and definitions consistent, and save the inputs used for each comparison.
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This page provides a calculation tool plus explanatory information so you can understand what the result means and when the underlying method may not fit your situation.