Water Heater Parts Explained: A Guide to Anatomy and Main Components

Water heater parts are integral to the functioning of these essential appliances, which provide a steady supply of hot water for various purposes. However, like any other device, water heaters can malfunction and require repairs or replacements over time.

Understanding the anatomy of a water heater can help you with DIY installation or replacements, ensuring system efficiency and reliability. This can save you money on energy bills and extend the lifespan of your water heater.

In this guide, we will explore the main components of a water heater, such as the gas valve, thermocouple, pilot light, and anode rods. We will also provide tips on how to install and replace them to keep your water heater running smoothly.

Combining these instructions with our troubleshooting guide can make repairing or replacing broken parts of a water heater easier.

It’s important to note that this article mainly reviews parts of gas and electric tank-type heaters, as they are the most common source of residential water heating. If you own a tankless heater, you can still use this article to learn more about the main tankless components.

Exploring the Main Gas and Electric Water Heater Parts

In addition to standard components, many advanced residential water heaters include components for efficient heating operation and increased safety, such as heat traps, powered draft hood, hot surface ignitor, flame arrestor, powered anode rod, and dry-fire protection. These components provide longer warranty, higher savings, comfort, and higher initial prices.

If you want to upgrade your water heater with quality elements to increase performance, efficiency, and the heater’s life, you can contact a professional plumber.

Storage Water Tank

Most water storage tank heaters feature tanks made of carbon steel, while some models, like the Rheem Marathon, use a plastic tank, and Westinghouse uses a stainless steel storage tank. This construction eliminates the need for an anode rod, corrosion protection, and frequent maintenance.

Due to the corrosive water action, water heaters equipped with metal tanks must include the glass/ceramic lining and anode rods.

The main purpose of the storage tanks is to store hot water. Tanks are wrapped in insulation so they can longer retain the hot water. And with the thicker insulation, the unit becomes more efficient. Typical insulation types are fiberglass and polyurethane foam that come with a thickness of 2 and 3 inches.

Gas Valve

Robertshaw, White-Rodgers, and Honeywell are among the most commonly used gas control valves for gas water heaters. The gas valve is the most important component of a water heater as it controls the delivery of natural or propane gas to the main burner and pilot light while also serving as a safety device.

The gas control valve also contains the thermostat. By turning the knob, you can increase or decrease the temperature of the hot water output. Gas control valves from the aforementioned manufacturers typically include a gas control knob, reset button, high water temperature limit safety, and temperature dial. Some advanced valves feature a diagnostic system for troubleshooting and more accurate temperature control.

If you need to replace a gas control valve, check out this guide on how to do it properly.

Heating Elements

Electric heating elements provide the heat in electric appliances and typically appear as the upper and lower elements on tall units. Smaller models often include just one element. These electric water heater parts also appear in solar heating systems and heat pumps used for backup heating.

To protect the electric elements, some water heaters feature the dry-fire protection, which safeguards the elements if they are exposed to air.

Use this article to get more information on replacing water heater elements.

Anode Rod (Sacrificial Anode)

The anode rod plays a crucial role in protecting the steel tank from corrosion, along with the tank’s glass or ceramic lining.

Often called a sacrificial anode, the rod sacrifices itself to extend the tank’s lifespan. Some models feature a powered anode that isn’t sacrificial, typically found on higher-end models.

Manufacturers make anodes from zinc, magnesium, or aluminum, and they install them at the top of the unit, making them easy to replace when needed.

Take a look at our comprehensive guide to learn everything you need to know about replacing an anode rod, including its impact on water heater performance, the best type to use, and common problems to watch out for.

Venting and Flue Pipes

The venting system exhausts the products of combustion through the flue baffle and vent pipes, and in some models, it draws in the fresh air needed for proper gas combustion.

You can choose from various types of venting systems based on your preferences, home design and construction, heater location, and other requirements.

These options include atmospheric, power, direct, and power-direct vent systems. Additionally, two-pipe closed combustion systems draw fresh air from outside the home, addressing issues caused by insufficient indoor ventilation.

You can also select from two-pipe or one-pipe atmospheric vent systems with a draft hood, or a concentric vent system, which uses two pipes (a pipe within a pipe) and can function with or without an electric-powered blower.

It’s essential to remember that different types of venting systems require different venting materials, such as stainless steel, PVC, or sheet metal.

Blowers

Electric blowers use a 110/120-volt electrical system, typically rated at 3 amps or less, and come equipped with a 6-foot cord.

Manufacturers usually install electric blowers on top of the water heater, where they push the exhaust and excess heat to the outside atmosphere.

Dip Tube

Dip tubes are an essential component of water heaters as they facilitate the flow of cold water into the tank.

They connect the cold water inlet and extend almost to the bottom of the tank, with about 6 inches of clearance. Different types of dip tubes are used, depending on the model and manufacturer.

For instance, Bradford White utilizes the perforated tube, which creates a turbulent flow that minimizes sediment and scale buildup. This results in maximized hot water output, providing you with more hot water for your daily needs.

The dip tube not only brings cold water into the tank but also allows water to circulate freely, reducing the risk of sediment buildup. As a result, the water heater’s performance improves, ensuring you always have hot water when needed.

Fortunately, replacing a dip tube is a simple process that you can easily do.

Gas Burner Assembly

Gas-powered appliances feature a crucial element known as the gas burner assembly, comprising multiple components:

Main burner. This is the heat source of gas water heaters, located below the storage tank. Advanced models from manufacturers such as Rheem, AO Smith, and Bradford White use eco-friendly burners that reduce NOx emissions by one-third compared to standard burners.

Orifice: When converting the water heater from natural gas to LP gas, replace the burner orifice.

Manifold Tube: This part includes the pilot burner/pilot light, the pilot tube, and the orifice. In water heaters with a pilot light, the pilot burner stays on after manual ignition and is used to ignite the gas. Some manufacturers use hot surface ignitors or electrodes instead of the pilot flame.

Igniter: A piezoelectric or hot surface igniter is used to light the gas.

Thermocouple: The thermocouple is a safety component that sends a signal from the pilot light to the gas control valve to manage gas delivery. It generates a small electrical current sufficient to signal whether the flame is present.

Thermopile: The thermopile functions like a thermocouple by converting heat into electrical energy. It consists of several thermocouples connected in series, which increases its ability to generate electricity.

If your water heater isn’t producing hot water, you may need to inspect and replace a thermocouple or a broken pilot light.

ECO

The ECO, or Energy Cut Off, is a critical safety feature in gas water heaters. It is a metal tube, also known as a temperature probe, mounted on the back of the gas valve and immersed in the water tank. Its primary function is to act as a high-temperature limit, ensuring the water temperature doesn’t exceed a safe level.

TCO

The TCO, or Thermal Cut Off Switch, is a resettable thermal switch designed to shut off the gas supply if the temperature of the combustion products becomes too high.

Thermostats

Standard residential water heaters commonly use mechanical thermostats, with factory settings typically set to 120°F to prevent scalding. However, these thermostats operate within a certain tolerance.

If you require assistance in replacing a thermostat on an electric water heater, refer to the instructions provided in this guide.

FVIR and Flame Arrestor (or Arrester)

The fireproof flame arrestor is part of the FVIR (Flammable Vapor Ignition Resistant) technology that prevents the accidental or unintended ignition of flammable vapors in water heaters Manufacturers typically build it into the base of the water heater using fire-resistant materials like stainless steel or ceramic. The flame arrestor blocks the flame from escaping the gas combustion chamber.

TPR Valve

The TPR valve, also known as the temperature and pressure relief valve, safeguards the water heater system from excessively high water temperature and pressure. It pairs with a discharge pipe that directs water to a suitable drain. Manufacturers factory-install these components, and code requires them for all tank-type water heaters.

If you notice that the valve is not functioning correctly, it is not advisable to attempt to repair it. Instead, use the step-by-step instructions in this guide to replace it yourself.

Drain Valve

Water heater drain valves appear on all types of water heaters and are typically made of plastic or brass. These valves are designed for draining, flushing, and maintenance.

We recommend using a brass drain valve because it is more durable and of better quality. Plastic drain valves are prone to damage, especially around the threads, making them more susceptible to leakage.

You can easily replace this part by following our step-by-step replacement guide.

Air Pressure Switch

The air pressure switch appears in gas water heaters that use an electric-powered blower to vent combustion products. It ensures the operational conditions are met in all power vent and power direct vent heaters.

Insulation

Manufacturers of hot water heaters use different foam thicknesses to provide various energy and heat waste savings, improved efficiency, and better performance. Some models come with high-quality insulation, such as 2″ or 3″ foam, while less efficient models may benefit from an insulation blanket.

Timers

Installing an electric water heater timer effectively reduces energy consumption and saves money. The timer turns off the water heater during periods of inactivity and turns it on when needed, providing significant cost savings over time.

Mixing Valves

Hot water mixing valves are commonly used in residential water heating for showering, bathing, and hand-washing. Their main function is to reduce the point-of-use temperature by mixing hot and cold water in the branch water line, providing a safe and comfortable temperature for the user. By installing a hot water mixing valve, homeowners can not only prevent scalding accidents but also save on energy bills by reducing the need for excessively high water temperatures.

Recirculating Pumps

If it takes too long to get hot water from your kitchen and bathroom fixtures, consider installing a recirculating pump. These pumps deliver hot water on demand, eliminating the need to wait for the water to heat up.

More advanced pumps include sensors and timers for better control, ensuring hot water is available exactly when and where it’s needed.

For a fully recirculating pump system, installers set up a loop from the water heater to the faucet and back, leaving no water inside the pipes. Alternatively, some systems use an existing cold water pipe to send unused water back to the water heater.

The main benefits of installing a recirculating pump include a continuous flow of hot water, hot water always being available at the point of service, and water and energy savings.

Expansion Tanks

Expansion tanks protect the water heating system by accepting excess water volume when water is heated and during high pressure inside the water heater. These tanks are used in closed systems and serve as safety devices.

Heat Traps

Heat traps are energy-saving elements connecting a water heater to the inlet and outlet water pipes but prevent the circulation of hot water within the pipes and heat loss. You typically find these on high-efficiency models.

When you install a water heater, use dielectric heat traps or fittings, as they feature a thermoplastic lining that prevents galvanic corrosion of the threads and further leakage.

How to Order Repair Parts

What you should know when ordering gas or electric water heater parts:

• Have the complete part number and description ready.
• Have the water heater model, series, and serial number ready.

Note: If any part of the water heater exposes to excessive moisture, contact a qualified service technician for repairs. If flood conditions submerge the water heater or any of its parts, including gas controls, the main burner, or the pilot light, replace the entire water heater.

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