Free Online Pond, Basin, and Tank Drain Time Calculator (Orifice)

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Pond, Basin, or Tank Drain Time — Orifice Outlet, Conic Volume Method


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Inputs
X
X
X
X
X
X
X
X
Results
Starting head, H1 ? Starting head, H1 ? X
Max flow, Qmax Max flow, Qmax X
Ending area, A2 ? Ending area, A2 ? X
Ending elevation check Ending elevation check X
Drained volume Drained volume X
Drain time (s) Drain time (s) X
Drain time (min) Drain time (min) X
Drain time (hr) Drain time (hr) X
Drain time (days) Drain time (days) X

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Notes

Formula
t = √H1 / (Cd Aor √(2g)) × (2Ax/5 + 8√(AxA0)/15 + 16A0/15) gives drain time from head H to the orifice. Drain time = t(H1,A1,A0) − t(H2,A2,A0), where H1 = starting elevation − orifice elevation, H2 = ending elevation − orifice elevation.
Method
The conic volume method models the pond or basin as a conic section between the starting area A1 at the initial water surface and the area A0 at the orifice centroid elevation. A2, the pond area at the ending elevation, is interpolated from A1 and A0 using the conic section model. Drain time from starting to ending elevation equals total drain time from H1 to orifice minus remaining drain time from H2 to orifice.
Derivation
Equation derivation
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