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Emptying time for tanks and reservoir.

Reservoir in emptying phase

To calculate the emptying time of a tank without the discharge pipe is quite simple, but mostly the reservoir is connected to a discharge pipe, in these cases is necessary to keep in advise also the pressure drop of the pipe.
The matter is that the pressure drop, in addition to the kind of pipe and fluid, is also influenced by the speed of the fluid passing through the pipe, which is determined by pressure which in turn is related to the level of the tank.

This application evaluates the time necessary executing a number of iterations, until it reaches a quite reasonably correct result. This system integrates Bernoulli's equation, the Colebrook and Whine methods and obtain the flow rate at the exit, at the end it calculates the emptying time.

Reservoir cylindrical Circular vertical
- Cylindrical
- Flat bottom

Reservoir rectangular or squared Rectangular or squared
- Parallelepiped
- Flat bottom

Useful diameter . . . D


Useful width . . . W


Useful depth . . . P


Starting level . . . h


Characteristic of the discharge pipe.

Internal diameter . . . d


(optional) Gap . . . h2


Total lenght


Kind of pipe

Absolute roughness internal wall

Wait roughness value


Characteristics of the fluid.

Selection of the kind of fluid

Viscosity at 20 ºC

Wait viscosity value


Density at 20 ºC


Waiting for calculation
Discharged litres l (dm3)
Emptying time s
Emptying time (equivalent) min
Relative roughness of the pipe r/d
Reynolds number (average) Re
Average friction factor (Colebrook Whine)
Data related to the maximum level . . . h
Maximum flow rate of the fluid l/min
Maximum speed of the fluid in pipe
Averaged data
Fluid flow rate l/min
Fluid speed in pipe

Back pressures and low pressions.
This software is not usable for cases when the tanks or the discharge pipes are subject to negative or positive pressure, it is developed for system at atmospheric pressure.

Curve, deviazioni e raccordi.
There are not options for pressure drop concentrated due to bends or other links, but they can equally be considered increasing the length of the pipe. For instance for normal bend it could be added a length of 4 times the envelope of the same bend.

Want to help us improve ?

The apps about tanks.

Calculation of the volume and level
for tanks or various containers.
Time needed to emptying a tank
or a reservoir containing a fluid.

The apps about pressure drop.

For air and other kind of gases,
(round pipe).
For air and other kind of gases,
(squared or rectangular channel).
For fluid at liquid state,
(general hydraulic plants).
Specific for oleodynamic plants.
Emptying time for a tank.