This diagram illustrate how in the Australian towns the rainwater is collected and processed for use it as drinking water.
Overall, initially the rain is collected from the gutter above the houses. Then a system of pipes guide the water trough a filter into a storage. After that, this need to be purified and with other pipes it is brought back to the houses as drinking water.
The water falled from the sky that has reached the top of an house is guided trough a drainage system by the gutter. Moreover, before the storage it is necessary to filter the rainwater beacuse the pipes could cointains other unexpected things.
At this stage, the dirty rainwater needs to be cleaned using chemicals for let it become drinkable. Now the water is pure and it is possibile to bring it back to the house as drinking water.