Please review my IELTS essay

The diagram shows how an Australian town collects rainwater in order to use for drinking water. Overall, rainwater can be purified and treated by chemicals through an order system. After the process, water will be supplied for inhabitants.
Originally, water is collected when it falls from the rooftop and flows into the gutter. It continuously runs down through the pipe in the side of the house into the drain which is linked to the whole system lying deeply under the ground.
After being gathered, Rainwater passes through the Water Filter to eliminate the impurities. It keeps on running to the Storage. From this position, it will be traversed through the tube to the Water Treatment Which processes the water with chemicals so that water is ensured to produce for people. After all processes, potable water will be pumped to each house and ready to use for daily demands.