Tank Drain Time Calculator
Time to empty a vertical tank through a bottom orifice (Torricelli, integrated).
Outflow slows as the head falls — emptying takes exactly 2× as long as it would at the constant initial rate.
Formula
Tank Drain Time Calculator is a free tank drain time for process, mechanical and water engineers — instant, accurate and 100% client-side, with the governing formula and reference shown next to the result so the number can be defended, not just quoted.
About Tank Drain Time Calculator
Time to empty a vertical tank through a bottom orifice (Torricelli, integrated). The calculation implements t = 2·A_t·√h₀ / (C_d·A_o·√(2g)) (Çengel & Cimbala, Fluid Mechanics, §5-4 (unsteady drain)). Outflow slows as the head falls — emptying takes exactly 2× as long as it would at the constant initial rate.
How to use Tank Drain Time Calculator
- 1Enter Tank diameter in m.
- 2Enter Initial liquid depth in m.
- 3Enter Orifice diameter in mm.
- 4Enter Discharge coefficient C_d.
- 5Read Drain time, Initial outflow instantly — no submit button needed.
- 6Need US units? Flip the SI/Imperial toggle and every field converts.
Why use Tank Drain Time Calculator?
- ✓Implements the standard formula — t = 2·A_t·√h₀ / (C_d·A_o·√(2g))
- ✓Reference cited on-page: Çengel & Cimbala, Fluid Mechanics, §5-4 (unsteady drain)
- ✓One-click SI ⇄ Imperial toggle — values convert in place, physics stays in SI
- ✓Live worked example: the substitution recomputes from your numbers
- ✓Runs entirely in your browser — nothing uploaded, free forever
Frequently asked questions
What formula does the Tank Drain Time Calculator use?+
It computes t = 2·A_t·√h₀ / (C_d·A_o·√(2g)), per Çengel & Cimbala, Fluid Mechanics, §5-4 (unsteady drain). The formula is displayed under the result along with a worked example substituted with your own inputs.
What should I keep in mind when using this calculator?+
Outflow slows as the head falls — emptying takes exactly 2× as long as it would at the constant initial rate.
Does this work for any fluid?+
Yes — density and viscosity are inputs (with common fluids suggested in the field hints), so the same physics applies to water, oils, gases and process fluids. Compute always runs in SI internally, so unit mix-ups can't corrupt the result.
Is the Tank Drain Time Calculator free to use?+
Yes — completely free, no sign-up, no limits. It runs client-side in your browser, so inputs stay private and results are instant even on slow connections.
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