Tank Filling Time Formula
How to calculate how long it takes to fill or drain a tank at a given flow rate.
The Formula
Fill Time (minutes) = Volume (Litres) ÷ Flow Rate (LPM)
Fill Time (hours) = Volume (m³) ÷ Flow Rate (m³/hr)
Examples
Example 1: 10,000 litre tank, 200 LPM pump
Fill Time = 10,000 ÷ 200 = 50 minutes
Example 2: 50 m³ tank, 12 m³/hr pump
Fill Time = 50 ÷ 12 = 4.17 hours = 4 hrs 10 min
Net Fill Rate (tank in use while filling)
Net Fill Rate = Fill Flow Rate − Consumption Rate
Fill Time = Volume ÷ Net Fill Rate
If you are filling a process water tank at 200 LPM while the process consumes 80 LPM, the net fill rate is only 120 LPM. Fill time = Volume ÷ 120, not ÷ 200.