Rooftop Rainwater Harvesting - how I have done

I collect from a rooftop area of about  380 square feet into the sump through filters. Using that calcuator, I get about 65,000 - 70,000 litres per annum. A rough figure from wastage from 'first flush' deducted. The sump capacity is about 7000 litres.  We will be using municipal water supply usually but during the regular rainy season, I stop the supply and utilize rainwater which keeps topping up the sump. See more.....