Arguably, the most common type of water heater is the traditional tank hot water heater. The unit consists of a storage tank that is designed to hold a fixed capacity of water, which in the U.S is typically rated in gallons. When the hot water tap from a faucet is opened, water flows from the top of the tank through piping to the faucet. As that water exits the tank, cold make-up water enters the tank near the bottom. As the cold water mixes with the hot within the tank, the temperature of the water in the tank begins to drop. When the temperature falls below the set temperature on the tank’s aquastat, the burner unit fires to begin reheating the water in the tank.
Standard tank water heaters are available in a variety of standard sizes to match the unit’s capacity to the hot water demands or consumption. Depending on the material used in the construction of the tank, the expected life can vary. Many units include a sacrificial anode to minimize corrosion of the tank components. Regular flushing out of sediment is recommended as part of the routine maintenance of traditional tank water heaters.