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Rainwater tank performance calculator: Input data


General data

Roof area (square metres)  
Nominal daily water demand (litres)  
Tank Size (litres)  


Rainfall data

Please enter ten years of monthly rainfall data (in mm) below. Each month should be followed by a comma. (e.g.74,58,106,195,164,103,104,104,128,127,120,67).

If you only have MEAN monthly rainfall figures, copy the same 12 figures into every row

Year 1:
Year 2:  
Year 3:  
Year 4:  
Year 5:  
Year 6:  
Year 7:  
Year 8:  
Year 9:  
Year 10:  

Rainfall data from this site is recorded for inclusion in a future look-up service. If you do NOT wish for your rainfall data to be added to this service check this box


Water management strategies

Three water management strategies are available. Choose from the following:

Constant demand

The user draws a set amount of water from the tank every day if there is enough in there to do so, otherwise the user takes what is left in the tank.


Varies with tank content

The user draws off an amount dependant on the volume of water in the tank. If the tank is between one-third and two-thirds full, the user takes the nominal demand that you specified from the tank. If the tank is more than two thirds full, the user draws off more water than usual, but if the tank is less than one third full, the user takes less water than normal. This water conservation means that system reliability is improved for a given tank size.


Varies with season

The user takes more water from the tank if it has rained recently and less when it has not. This aids water conservation and increases system reliability for a given tank size.
Note: This option may take over a minute to process - please be patient before hitting the "stop" button.