Get matched with top water heater pros in Excel, AL

Water expands when heated and also when freezing. When water is heated, it expands by around 4%. For a full water heater, this is one of the main reasons malfunctions occur—the hot water has nowhere else to go but out. Due to the constant expansion and reduction in volume, it’s recommended (required in most places) that an expansion tank be installed.

Unless they are connected to the same system, boilers and water heaters will both need their own expansion tanks. The only case they wouldn’t have separate expansion tanks is if the boiler is pulling double duty and managing a heating system while also supplying hot water for a home. In which case, you may not need a hot water heater.

No, boilers and water heaters are not interchangeable because they serve different primary functions. Boilers are used for central heating systems, providing hot water or steam to heat your home. In contrast, a water heater's purpose is to supply hot water for daily household use, such as for faucets and showers. A water heater alone cannot supply the warm water or steam needed for a central heating system.

While they are not interchangeable, it is common to have both a boiler and a water heater. In fact, a conventional boiler often works best when a water heater system is already in place. The two systems can be combined to provide both heating and hot water, either by pairing a boiler with an indirect water heater or by installing a premade combination boiler-water heater unit. For home heating, some homeowners may also opt for a furnace instead of a boiler.

No state requires you to vent an electric water heater. Other installation requirements for water heaters will vary, though, depending on the state and local jurisdiction in which you live. Some places require permits, while others don’t. Some may force you to place the appliance a certain distance from any walls or other appliances, while others don't. When you find a local professional to install a water heater, this expert will ensure you follow all the local regulations.