To find the right storage tank size, it is necessary to get an idea about the rainwater yield per year and the water demand.
Storage tank size can be selected using the following criteria:
If the yield < requirement, then a storage volume of 3% of the average annual rainwater yield.
If the yield = requirement, then a storage volume of 5% of the average annual rainwater yield.
If the yield > requirement, then a storage volume of 5% of the average annual rainwater yield.