How to Install and Replace Various Water Heater Parts (Exploring the Main Components)

Explore hot water heater parts and accessories found on electric and gas water heating appliances for easier order and purchase.

A better understanding of the heater's components such as the gas valve, thermocouple, pilot light, venting system, and others makes it much easier to troubleshoot and fix the problem.

Using the instructions found here and combining them with our troubleshooting guide it gets easier to repair or replace the broken parts.

This article reviews mainly parts of the storage gas and electric tank heaters as the most common source of residential water heating.

If you are the owner of a tankless heater, use this article to learn more about the main components.

The main gas and electric water heater parts

Gas water heaterGas water heater
Electric water heaterElectric water heater

As we can see in every residential water heater design, some components are standard, while others are there for efficient heating operation and increased safety. Good examples are the heat traps, powered draft hood, hot surface ignitor, flame arrestor, powered anode rod, and dry-fire protection. Such a difference provides a longer warranty, higher savings, comfort, and greater initial prices.

You can even contact a professional plumber and upgrade your water heater with quality elements increasing the performance, efficiency, and heater's life.

Storage water tank

Gas water heater insideGas water heater

The majority of the water storage tank heaters are equipped with tanks made of carbon steel, while some models, such as Rheem Marathon, utilize a plastic tank, or Westinghouse uses a storage tank made of stainless steel. Such a construction automatically 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

Gas valveGas valve

Robertshaw, White-Rodgers, and Honeywell are three of the most popular gas control valves and are found on the majority gas water heaters.

The gas valve is the heart of the water heater as it controls the delivery of the natural or propane gas to the main burner and pilot light and is also designed as a safety device.

Since the thermostat is part of the gas control valve, by turning the knob, you can increase or decrease the temperature of the outgoing hot water.

Gas control valves from the above manufacturers have similar elements like the gas control knob, reset button, high water temperature limit safety, and temperature dial. More advanced valves are those that have a diagnostic system for troubleshooting and more accurate temperature control.

See how to replace a gas control valve here.

Heating elements

Heating elementHeating element

Electric heating elements are the source of heat on electrical appliances and are usually found as the upper and lower elements on tall units.

Smaller models are often equipped with only one element. These electric water heater parts can also be found in solar heating systems and heat pumps used for backup heating.

In addition to the electric element protection, some water heaters are equipped with the dry-fire feature, protecting the elements if exposed to the air.

More information on replacing water heater elements here.

Anode rod (sacrificial anode)

Anode rodAnode rod

The anode rod protects the steel metal tank from corrosion, together with the tank's glass or ceramic lining.

The element is usually called the sacrificial anode, as it sacrifices itself to extend the tank's life. The powered anode is not sacrificial and is found on better models.

Anodes are typically made of zinc, magnesium, or aluminum installed on the top of the unit and can be easily replaced.

See how to replace an anode rod, how it can affect the water heater performance, which type is the best, and what the common problems are. 

Venting and flue pipes

Power VentPower Vent

The venting system is designed to vent the products of combustion out through the flue baffle and vent pipes, and in some models, to draw the fresh air needed for proper gas combustion.

Based on your preference, home design and construction, the location of the heater, and other requirements, you can find different types of venting systems; atmospheric, power, direct, and power direct vent, also:

  • Two-pipe closed combustion system that eliminates problems caused by the insufficient indoor ventilation, while it draws the fresh air from outside the home.
  • Two-pipe or one-pipe atmospheric vent system with the draft hood.
  • Concentric vent system - consists of two pipes (pipe within the pipe); where the larger pipe is used to draw the air in, and inside pipe designed to direct the gases out. It can be used with or without the electric-powered blower.

Remember that different types require different venting materials, including stainless steel, PVC, or sheet metal.


The electric blowers use a 110/120-volt electrical system, usually rating 3 amps or less, and are equipped with a 6-foot cord.

Electric blowers are typically installed on top of the water heater from where it pushes the exhaust and excess heat to the outside atmosphere.

Dip tube

Dip tubeDip tube

Dip tubes are designed to bring the cold water inside the tank.

They connect the cold water inlet and extend almost to the bottom of the tank (approximately 6" clearance). There are different types used, which depend on the model and manufacturer. For example, Bradford White utilizes the perforated tube to create the turbulent flow and reduce the scale and sediment buildup, resulting in the maximized hot water output. It is usually made of PEX polymer.

The primary purpose of the dip tube is to allow cold water to enter the bottom of the tank. Since hot water tends to rise to the top and while cold water enters at the bottom, water inside the tank can freely circulate, reducing the risk of sediment buildup.

Dip tubes are easy to replace.

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Gas burner assembly

One of the essential parts found on gas-fired appliances is the gas burner assembly, consisting of several components:

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

Orifice. The burner orifice should be replaced when converting the water heater from natural to LP gas.

Manifold tube. It consists of the pilot burner/pilot light with the pilot tube and orifice. On water heaters with the pilot light, a pilot burner remains ON once it is manually lit. It is used to ignite the gas. Some manufacturers utilize the hot surface or electrodes instead of the pilot flame.

An igniter like a piezoelectric or hot surface is used to light the gas.

Thermocouple. A thermocouple is the safety part used to send the signal from the pilot light to the gas control valve to control the gas delivery. A small electrical current is generated, which is enough to signal if the flame is present or not.

A thermopile does the same thing as the thermocouple - converting heat into electrical energy, but is composed of a few thermocouples connected into series, increasing the unit's ability to produce electricity.

If your water heater is not producing hot water, you might want to inspect and replace a thermocouple or a pilot light , if broken.


The ECO or Energy Cut Off is the metal tube (temperature probe) mounted onto the back of the gas valve and immersed inside the water tank. It acts as the temperature high limit.


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


Mechanical-type thermostats are used on standard residential water heaters. Thermostats are usually factory set to 120 F to prevent scalding water, and they operate with a certain tolerance.

If you need help replacing a thermostat on an electric water heater, just follow the information found in this guide.

FVIR and flame arrestor (or arrester)

The fireproof flame arrestor, built in the water heater base, is part of FVIR or Flammable Vapor Ignition Resistant technology that deals with flammable vapors' accidental or unintended ignition. It is made of fireproof material such as stainless steel or ceramic, and it blocks the flame from escaping the gas combustion chamber.

TPR valve

TPR valveTPR valve

The TPR valve or temperature and pressure relief valve is used to protect the system from excessively hot water pressure and temperature. It is usually combined with the discharge pipe to an adequate drain. These elements are factory built-in and are code on all tank-type water heaters.

If the valve stops operating properly, don't try to repair it, use these DIY instructions to replace instead.

Drain valve

Drain valveDrain valve

Water heater drain valves are found on every water heater and are made of plastic or brass. Drain valve are designed for draining, flushing, and maintenance.

The recommendation is to use one made of brass as they are more durable and have better quality, while plastic drain valves are easy to damage, especially around the threads making them more likely to leak.

This is another simple water heater part that is easy to change, just use this step-by-step replacement guide.

Air pressure switch

An air pressure switch is used on all gas water heaters using the electric-powered blower for venting products of combustion. It is used for all power vent and power direct vent heaters to verify that operational conditions are met.


Different foam thicknesses around the tank will provide more or less savings in energy and heat waste, efficiency, and performance improvement. This is why some manufacturers are designing hot water heaters with 2" or 3" high-quality insulation, while on the low efficient heaters, it is recommended to use an insulation blanket.


Electric TimerElectric Timer

One of the great ways to reduce energy consumption and save money is to install an electric water heater timer. A water heater timer is designed to turn the water heating off during periods of inactivity and turn it on when needed.

Mixing valves

Hot water mixing valves are used in residential water heating; for showering, bathing or hand-washing, to reduce the point-of-use temperature by mixing hot and cold water in the branch water line.

Recirculating pumps

If it takes too long to get hot water in the kitchen and bathroom fixtures, install a recirculating pump. Circulation pumps are designed to deliver hot water on demand. Better pumps include sensors and timers for better control.

You can get a fully recirculating pump system with a loop from the water heater to the faucet and back, leaving no water inside the pipe.

There is also a system that utilizes an existing cold water pipe to send the unused water back to a water heater.

The main benefits of installing a recirculating pump are that you will get a continuous flow of hot water, water is always hot (ready) at the point of service, water, and energy savings.

Expansion tanks

Expansion tanks are designed to 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 on closed systems and are considered safety devices.

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 has been exposed to excessive moisture, you should contact a qualified service technician for the repair. If the water heater has been subjected to flood conditions or any of its parts, including gas controls, the main burner, the pilot light, was submerged in water, an entire water heater should be replaced.

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