Rainwater is much better then potable water for irrigation, because of the lack of chlorine and other chemicals used in potable water treatment. Plants thrive with irrigation using stored rainwater and may grow 20%-30% more using rainwater then traditional municipal water or ground water.
Rainwater is valued for its purity and softness. It is slightly acidic, and is free from disinfection by-products, salts, minerals, and other natural and man-made contaminants. Appliances last longer when free from the corrosive or scale effects of hard water , laundries use less soap and vehicles do not need to be dried to eliminate spotting.
Rainwater is much cleaner then the surface water we store in our lakes. By collecting it before it hits the ground or soaks into the ground most of the non-source pollution is eliminated.
About 70% of the Earth is covered with water, and 96.5% of that is part of the salty oceans. Only a small portion of the Earth’s water is freshwater. 1.7% is below ground and 1.8% is above ground in ice caps, glaciers and permanent snow. with only .06% usable above ground in lakes rivers and swamps.