Rainwater tanks are containers that hold water runoff from roofs, patios, and other surfaces from which rain can be collected and stored for later use. The tanks can be made of many different materials, including wood, metal, polyethylene, fiberglass, and concrete. The uses of the rainwater collected in rainwater tanks are many. The water may be used for watering gardens, flushing toilets, running washing machines, and — with filtration — for drinking and cooking. Rainwater tanks are also known as rain barrels in the United States or water butts in the United Kingdom. They are widely used in arid parts of Australia and in developing countries as well.
The simplest form of a rainwater tank is probably an old oak barrel, or other similar container that collects rainwater at a downspout or at a chain which the water runs down. Usually this type of rainwater tank is used for garden watering. More complex forms of rainwater tanks include those that are embedded in a slab, possibly under a house, for instance, or incorporated as part of the heating and cooling of a building structure.
More complex rainwater tanks and collections systems tend to be the ones which are used in multiple ways. The water in them may be used for cooling a building during the hotter months. It may also be filtered to provide fresh drinking water or used for flushing toilets and running the washing machine — or perhaps for all of the uses listed, and more.
The biggest maintenance issues with rainwater tanks center around keeping them free of dirt and debris. Often this is accomplished with the use of some sort screen or mesh on the top of a simple rainwater tank. Algae and sludge buildup in the tank can also present a maintenance issue. For this reason, the tanks should be cleaned periodically. Sometimes special filtration systems are utilized, especially in cases where obtaining drinking water is desired.
Rainwater tanks can be an environmentally friendly way of living within the limits of the ecosystem in which they are utilized. Then can keep the water that falls in the area from running off and causing erosion. They may also help to return that water slowly to local aquifers, streams, and rivers.
From a historical perspective, rainwater tanks are not a new phenomenon. They have been around since the time of the ancient Romans and Egyptians, mainly in the form of cisterns. Many cultures have used cisterns to collect rainwater in wetter seasons to provide themselves with water in the dry seasons.