ToolnozaTank fill-time formula
Time = (tank capacity − current volume) ÷ net flow. Net flow = inflow rate − outflow rate. With litres and litres per minute, the answer is in minutes; divide by 60 for hours.
Example: filling a 1,000 L tank
A tank holds 1,000 L and currently contains 200 L. Inflow is 20 L/min and outflow is zero. Remaining volume is 800 L, so 800 ÷ 20 = 40 minutes. If outflow is 5 L/min, net flow is 15 L/min and the estimate becomes about 53.3 minutes.
Use remaining capacity and net flow
Enter the tank’s total capacity and the amount already inside, not the amount to add as capacity. Subtract any simultaneous outlet flow from the inlet. Use compatible units, such as litres with litres per minute or gallons with gallons per minute.
Assumptions and real-world variation
The estimate assumes a constant flow rate, no unentered leaks and a known current volume. Actual filling may slow with changing pressure, pump performance, pipe restrictions or a float valve. If net flow is zero or negative, the tank will not fill under those inputs.
Frequently asked questions
How long does 800 L take at 20 L/min? 40 minutes if there is no outflow. What if the tank is partly full? Subtract its current contents from total capacity first. Does the result include pump changes or leaks? Only an outflow value that you enter; changing flow is not modelled.