Hot Water Heater Parts 
Installation and Replacement Tips

A review of the main hot water heater parts found in the electric and gas-powered tank-type heaters and from the top manufacturers in North America. This list will help you in troubleshooting the problem and when ordering the part.

Gas water heater parts

Gas water heaterGas water heater

Temperature and pressure relief valve

The temperature and pressure relief valve or TPR valve is the safety component that must be properly sized and installed. The element is designed to relieve the excess pressure when it exceeds the maximum allowed. When you buy a brand-new heater, the TPR valve is factory installed or provided.

The opening for this part may be on the side or top of the unit, and the installation usually requires the drain line so it can discharge the excess water into the floor drain.

Anode rod

The anode rod or sacrificial rod protects the metal tank from the aggressive water action or corrosion. It is submerged in the water, and it sacrifices itself to protect the metal tank and extend the life of the water heater.

Most of the manufacturers are using the magnesium type rod, but there are some, which will use aluminum, zinc, or powered-type.

Dip tube

The dip tube is a non-metallic tube found under the cold-water inlet connection, where the cold water enters the tank, transferring the cold water to the bottom of the tank. Some manufacturers are designing dip tubes in a way to generate a turbulent flow and reduce the sediment build-up within the heater.

This system is known as the self-cleaning system. One of the main problems of the dip tube is when it deteriorates resulting in insufficient hot water production.

Gas burner

The gas burner is part of the burner assembly, which consists of the main and pilot burner with orifices, supply tubes, and thermocouple. A properly operated gas burner should produce a light-blue flame with the yellow tips.

Combustion chamber

The combustion chamber is factory sealed, and this is the place where the gas burner is located and where the gas burns. Some manufacturers include the sight window so you can check the combustion process.

Venting system

Water heaters with the atmospheric venting utilize a single pipe to remove the exhaust gases outside while the air for combustion is usually taken from the surrounding air. Some models also use the power-vent system and its powered blowers to remove the exhaust gases out and draw the fresh air in for the gas combustion.

Pilot light

If the water heater is equipped with the pilot assembly, the pilot can be lit either manually or by a piezo-electric spark, which further ignites the main gas burner. The pilot remains ON once it is lit.


The thermocouple is another safety element, which is designed to determine if a pilot light is present, and will shut the water heater OFF if the pilot or burner flame is not lit. As part of the FVIR system, TCO or thermal cutoff device is integral with the thermocouple that shuts the unit OFF when activated.

Thermal switch

The thermal switch is the safety element which shuts down the pilot light and the main gas burner if there is an excessive temperature increase in the combustion chamber when the pilot is extinguished and if there is a restriction in the airflow.


Most of the water heaters are equipped with the metal tank covered with the glass/porcelain lining for protection against corrosion. But, there are some manufacturers, such as Marathon - Rheem that is building heaters with the plastic tanks, which makes them lighter and resistant to some usual problems such as the rotten egg odor.

Flame arrestor plate

The flame arrestor plate prevents any accidental ignition of the flammable vapors when they are present in the air and flowing into the combustion chamber. It is made of the fireproof material and is built into the base of the water heater.

Gas control valve and thermostat

The gas control valve is the heart of the gas heater and safety element which delivers gas to the pilot and main burner. It has the thermostat attached to set and control the temperature.

Drain valve

The drain valve is located at the bottom of the heater and is used to drain water from the tank. This is especially important when draining to reduce the sediment build-up or during freezing temperatures.

Heat traps

Heat traps are energy-saving elements that are connecting a water heater to the inlet and outlet water pipes but prevent the circulation of hot water within the pipes and heat loss. These are usually found on high efficient models.

When installing a water heater, it is recommended to use dielectric heat traps or fittings as they are built with the thermoplastic lining, therefore, preventing the galvanic corrosion of the threads and further leaking.

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Electric water heater parts

Electric water heaterElectric water heater

The following parts are specific for electric heaters, while others can also be found in the above section.


Every electric water heater is equipped with the adjustable and surface mounted thermostats, which respond to temperature change in the heater and allow you to set and control the temperature of the outgoing water. A high-temperature limit or ECO is part of the assembly, and it prevents the water temperature increase extremely high.

Thermostats are factory set at 120 F, as the energy efficient setting and to avoid the risk of scalding, but can be changed by using the screwdriver on the dial. Each heating element has its own thermostat. The upper thermostat controls the heat generated by the upper and lower heating element, where the last one provides the main heat supply.

Heating element

The heating element is one of the most important water heater parts and is directly involved in efficient water heating. Units with the capacity of over 30 gallons are equipped with the upper and lower elements, while smaller tank sizes have only one element.

They can operate in Simultaneous and Non-Simultaneous modes. Heating elements and its thermostats are located behind the access panels.

Electrical junction box

Electrical junction box allows you to connect the power-supply wiring to the wires inside the heater.

Other water heater parts that you might find as part of the system are:

Insulation blanket

Insulation blankets are recommended for both electric and gas-powered water heaters, and they help in reducing the standby heat loss and keeping the water hot longer. It is not needed for high-efficiency units, as the foam insulation is already thick enough and has the high R insulation value.

Thermal expansion tank

Thermal expansion tanks are used in closed water heating systems for the frequent relief of thermal expansion and to avoid the heater damage.

Drain pan

The drain pan is installed under the water heater to prevent damages due to leaking. It must be correctly sized and piped, usually to the floor drain. Metal pans can be used for both gas and electric water heaters, while plastic pans only for electric.

Hot water mixing valve

The hot water mixing valve mixes the cold and hot water and provides the optimum temperature that prevents scalding burns, especially among kids and older people.

How to order parts

If planning to order any of the above water heater parts, you must know the model number and a serial number of your water heater. This information can be found on the label of the heater.

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