Rain Barrel Fill Time
Determine how long a rain barrel needs to reach capacity with a given fill rate. The calculator outputs a clear hours–minutes–seconds breakdown so you can schedule watering, irrigation top-ups, or pump shutoff timers.
Monitor filling in person and follow local regulations on rainwater storage and overflow handling.
Examples
- 200 L barrel at 12 L/min ⇒ about 16 min 40 s to fill.
- 1,000 L IBC tote at 25 L/min ⇒ roughly 40 min.
- 95 L barrel at 8 L/min ⇒ around 11 min 53 s.
FAQ
Can I enter gallons instead of litres?
Yes—convert gallons to litres first (US gallons × 3.785, UK gallons × 4.546). Using consistent units keeps the output accurate.
What if my flow rate fluctuates?
Use the average flow or re-run the calculation with the slowest expected rate to build in safety margin.
Does the tool account for head height or pump curves?
Not automatically. Measure actual delivered flow at the barrel inlet, since pump performance changes with elevation and hose length.
Additional Information
- Formula: Fill time (minutes) = Barrel volume ÷ Flow rate. The tool converts the decimal result into hours, minutes, and seconds for easier scheduling.
- Flow rates vary with water pressure, hose diameter, and elevation. Measure actual delivery rather than relying on nominal hose ratings.
- Consider shutting off pumps a minute early to prevent overflows, especially if debris or filters slow the flow mid-fill.
- For roof harvesting, estimate flow by multiplying rainfall intensity (mm/h) by roof catchment area (m²) and by runoff coefficient (typically 0.8–0.9).