Tank Drain Time Calculator
Estimates the ideal emptying time of a constant-area tank. Changing an entry recalculates the displayed result immediately.
Define the fluid state
Drain time
Where this relationship is useful
Estimates the ideal emptying time of a constant-area tank. The inputs describe tank area, outlet area, initial liquid depth, gravitational acceleration, and the reported unit is s.
A changing tank cross-section, discharge coefficient, pipe resistance, or nonzero final depth changes the draining equation.
On the tank drain time page, each number stays beside its physical unit. That pairing matters because a converted value placed in an unconverted field can look plausible while changing the model.
Working through tank drain time
Begin with t = (At / Ao)√(2h / g) and identify the sought quantity before substituting. The sample entries give a concrete calculation that can be repeated by hand.
Write the tank drain time relation before touching the numbers. This exposes an inverted ratio or omitted conversion while drain time can still be traced to its source.
Checking the sample Tank Drain Time condition
The starting example uses Tank area = 2 m²; Outlet area = 0.01 m²; Initial liquid depth = 3 m; Gravitational acceleration = 9.80665 m/s². Entering those values provides a baseline before testing a different physical condition.
After calculating, rearrange t = (At / Ao)√(2h / g) for one supplied quantity and see whether it returns the original entry. This reverse check is especially helpful when powers, ratios, or reference values are present.
Two ways to audit the arithmetic
Reduce the units in t = (At / Ao)√(2h / g); the surviving dimension must agree with s. If it does not, the arithmetic should not be accepted even when the displayed number is finite.
Then vary one measured input by ten percent and predict whether drain time should rise, fall, or remain unchanged. That sensitivity test is independent of merely repeating the same keystrokes.
Where Tank Drain Time stops being sufficient
The calculation assumes steady incompressible flow and the geometry printed beside the inputs. Storage, leakage, cavitation, or an omitted loss coefficient requires a broader balance before accepting drain time.
Treat that boundary as part of the tank drain time result rather than hiding it in a correction applied afterward.
Carrying drain time into later work
Do not round an intermediate tank drain time value merely to match the display. Retain guard digits, then report drain time at defensible measurement precision.
Record the formula, units, geometry, and material state with drain time. A bare number cannot reveal whether density, pressure reference, flow area, or operating condition was interpreted correctly.
Continue from drain time
From here, compare torricelli efflux speed calculator and reynolds number calculator.
Continue only with a relationship whose physical scope matches the Tank Drain Time setup.
Checking the Tank Drain Time result
What does the drain time represent?
It is the output of t = (At / Ao)√(2h / g) for the field definitions and units printed on the tank drain time page.
How can I check the drain time?
Rearrange t = (At / Ao)√(2h / g) to recover one input, and independently confirm that the remaining dimension reduces to s.
Must all entries use the displayed units?
Yes. Convert every measurement to the unit beside its field before applying the tank drain time relationship.
Why could another drain time differ?
A different material state, geometry, reference condition, rounding rule, or model assumption can change the reported drain time.