Fact Checked

What Is Water Heating?

David Bishop
David Bishop

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.

A water heater.
A water heater.

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 used in washing machines is heated by using a water heating system.
Water used in washing machines is heated by using a water heating system.

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.

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Discussion Comments


Like this article says, the hot water heating systems without tanks save you money in the long run, but it is inconvenient when you have to wait for the water to heat up. With our old gas heater, we never ran out of hot water and we could set the control based on how many people we had in the house and how much hot water we thought we would need. I'm not sure the savings are worth the inconvenience we have to put up with, with our new tankless hot water heating system.


@Feryll - Some of the old hot water heaters can be a challenge to light, but the biggest problem is that you have to overcome your fear of gas. The heaters are actually very safe. As this article explains, gas heat is more popular than electric heat for heating water. If gas were not safe then fewer people would be using it.

Your heater should have a step by step list of directions attached to the outside of the heater somewhere. Since this is an old heater the directions may be worn and you may have a difficult time reading them, but they should be there. Also, the next time you have gas delivered, you should ask the person making the delivery to talk you through the process of lighting the heater. There is a good chance that sooner or later you will have to light it.


We just bought a new house, actually it is an old house, but it is new to us. Anyway, it is set up with a natural gas heating system and an old gas hot water heater. Neither me or my girlfriend have ever had a gas hot water heater. I feel safer with the electric heaters. If the pilot goes out on the heater then I am not sure I can get it lit again. How difficult are they to light?

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    • A water heater.
      By: scaliger
      A water heater.
    • Water used in washing machines is heated by using a water heating system.
      By: Rasulov
      Water used in washing machines is heated by using a water heating system.
    • Electric water heaters are quiet and energy efficient.
      By: EuToch
      Electric water heaters are quiet and energy efficient.