Water heating is a system of warming and transferring water throughout a building to sinks, showers, baths, washing machines and dishwashers. The water is usually heated and stored in a device known as a water heater, which typically uses electricity or fossil fuels to warm the water. Once heated, the water can be distributed as needed throughout the building to bathrooms, kitchens and laundry rooms. In some buildings, heated water also may be used to provide radiant space heating, usually with a system of small pipes installed into the flooring. Heated water also has many applications in manufacturing and other industries.
Most domestic water heating in the United States uses natural gas as the fuel source for the water heater. Natural gas is typically pumped directly to the consumer’s home through a series of underground pipelines. The gas is then ignited at the base of the water heater, and heat from the flame gently warms the water held inside the reservoir. Electricity is the second most popular method of water heating in the United States, particularly in areas that do not have the infrastructure to support natural gas delivery. Some regions may use other types of fossil fuels, solar power or geothermal energy to heat water for domestic or industrial use.
While most traditional water heater designs utilize a hot water tank to store water until needed, other models — known as tankless heaters — operate by instantly heating water either at the tap or at a central position in the building. These types of systems operate more efficiently than a traditional water heater and can conserve both water and energy. Tankless heaters can take longer to provide hot water, because the water is not being warmed continuously. They also are generally more expensive than traditional units in some areas.
Water heating also has been used for radiant space heating in buildings with a system known as hydronic heating. This system operates by pumping hot water through a series of small tubes in the floor. This warms the air near the floor, and that air rises and heats the entire room. The heated flooring also is more comfortable to walk on during the winter months, particularly in the bathroom. While this system can offer greater energy efficiency and better air quality than other common heating methods, the tubes are vulnerable to leaking and air bubbles getting in to the system.