Galvanized Steel Cisterns
Cisterns are commonly prevalent in areas where water is scarce, either because it is rare or has been depleted due to heavy use. Historically, the water was used for many purposes including cooking, irrigation, and washing. Present-day cisterns are often used only for irrigation due to concerns over water quality. Cisterns today can also be outfitted with filters or other water purification methods when the water is intended for consumption. It is not uncommon for a cistern to be open in some manner in order to catch rain or to include more elaborate rainwater harvesting systems. It is important in these cases to have a system that does not leave the water open to algae or to mosquitoes, which are attracted to the water and then potentially carry disease to nearby humans.
Some cisterns sit on the top of houses or on the ground higher than the house, and supply the running water needs for the house. They are often supplied not by rainwater harvesting, but by wells with electric pumps, or are filled by manually or by truck delivery. Very common throughout Brazil, for example, they were traditionally made of galvanized metal or concrete walls (much like the houses themselves), with a similar concrete top (about 5 cm thick), with a piece that can be removed for water filling and then reinserted to keep out debris and insects. Modern cisterns are manufactured of galvanized steel or plastic: in Brazil with a characteristic bright blue color, round, in capacities of about 10,000 and 50,000 liters. These cisterns differ from water tanks in the sense that they are not entirely enclosed and sealed with one form, rather they have a lid made of the same material as the cistern, which is removable by the user.
To keep a clean water supply, the cistern must be kept clean. It is important to inspect them regularly, keep them well enclosed, and to occasionally empty and clean them with a proper dilution of chlorine and to rinse them well. Well water must be inspected for contaminants coming from the ground source. City water has up to 1ppm (parts per million) chlorine added to the water to keep it clean, and in many areas can be ordered to be delivered directly to the cistern by truck. If there is any question about the water supply at any point (source to tap), then the cistern water should not be used for drinking or cooking. If it is of acceptable quality and consistency, then it can be used for (1) toilets, and housecleaning; (2) showers and hand washing; (3) washing dishes, with proper sanitation methods, and for the highest quality, (4) cooking and drinking. Water of non-acceptable quality for the aforementioned uses may still be used for irrigation. If it is free of particulates but not low enough in bacteria, then boiling may also be an effective method to prepare the water for drinking.
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