A rainwater tank (sometimes called a rain barrel in North America in reference to smaller tanks, or a water butt in the UK) is a water tank used to collect and store rain water runoff, typically from rooftops via pipes. Rainwater tanks are devices for collecting and maintaining harvested rain. A rainwater catchment or collection (also known as "rainwater harvesting") system can yield 2,358 litres (623 US gal) of water from 2.54 cm (1.00 in) of rain on a 92.9 m2 (1,000 sq ft) roof.