The network of pipes and plumbing fixtures that a typical home uses is a complex system that results in hot and cold water, on demand, throughout the home. In some cases the system includes a water storage tank, cistern or cold water tank located on the roof or within the roof's structure in the attic. This location is best for several reasons, depending on the home's layout and the water tank's purpose.
In many cases, a water storage tank is located in the roof because it is the highest point in the building. Placing a water storage tank at a high elevation allows it to use gravity to feed other water tanks, faucets and fixtures below. For example, a home with an attic cold water tank can use a pump to fill the tank, then use gravity to fill toilets, sinks and a hot water tank elsewhere in the home. The water will continue to flow out of the tank due to gravity even if the power goes out.
Some homeowners seek to conserve water by harvesting it in rooftop or attic-mounted tanks. Water-harvesting systems attach to gutters and collect the rain water that falls on a roof, diverting it to a collection tank where it can flow into a filter for household use or be used for watering plants at a later time. While water harvesting can also use rain barrels and other types of tanks mounted on the ground, a roof tank saves on the need for piping.
Another type of water tank that is likely to be located in the roof is a tank for a solar water-heating system. These tanks are connected to rooftop solar panels, which use heat from the sun to heat water in the tank. This hot water reduces the need to burn natural gas or draw electricity from the public utility grid for warm showers, sinks, the washing machine and dishwasher. Solar water-heater tanks in the roof also have the benefit of elevation, allowing them to feed fixtures below through gravity.
The roof can be an appealing location because of space considerations. Homes without basements lack an obvious spot for a hot water tank, while the space on a roof or within an unfinished attic is likely to go at least partially unused. Water tanks in the roof do present a risk of flooding if they, or the pipes that they are attached to, rupture, but they keep water stored out of the way and provide more storage space in a home's living areas.
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