The picture below represents the process of collection and treatment of rainwater in a town in Australia to use it for drinking purposes. Overall, there are seven steps from the inital to final stage, where the water is cleared from being impure to pure.
Primarily the water that starts pouring on all the households are accumulated in a common outlet to the drain, which then passes down the pipes to the water filter. The filter has three smaller sections. The liquid moves to the storage tank from the filter and eventually is passed on to the treatment container for purification. Chemicals are used to disinfect the water and comes from an outlet above it.
The treated water is pumped up the pipes and supplied to every house in the locality by a similar route to the collection, hence harvesting and reusing the water that comes from rain. The final product is then used for drinking.