Water Tanks as Storage Devices

Water tanks are devices storing harvested rain from roofs. Rainwater tanks are installed to make use of rain water for later use, reducing one’s reliance for mains water both for economic and environmental reasons but especially to aid self-sufficiency.
Rain is really distilled water precipitating after condensing at high altitude where temperatures are low. It matters not whether water falling from the sky is rain, hail, sleet or snow, it is all water and may be harvested.