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Parts of a Water Heater: The Complete Guide

Parts of a gas hot water heater

Table of Contents

Life today is full of all the trappings of modern convenience, including something many of us almost take for granted – nearly instant hot water available on demand. Water heaters usually don’t come to anyone’s mind until they’re suddenly not working. But how do we keep these critical household systems maintained and always working their best to avoid this? Step one is for homeowners to understand all the parts of a water heater and how they work.

Knowing the parts of your water heater and how they function helps you to pinpoint and address any potential issues that might arise, staying on top of the troubleshooting, routine maintenance, and general safety of your equipment. Let’s take a deeper look at this critical household system and learn more about the inner workings of the 4 most common types of water heaters.

Tank Water Heater  

A tank water heater is the most common type of water heater. It has a large tank to hold hot water until needed. Some of the most common components you’ll see on a tank water heater include:


A tank water heater is the most common type of water heater. Tank water heaters are composed of an insulated tank, which varies in size depending on the needed amount of water to heat a home.

Heating Element  

A conventional tank water heater can be heated by two different methods: natural gas or electricity. In the electric tank water heater, a heating element is used to generate heat within the water heater. A heating element is a metallic rod that is immersed in the water inside the tank. An electrical current passes through the heating element, generating heat for the water heater to work. This process is similar to how a toaster works. In most water heaters, you can find two heating elements – this allows your water heater to heat your home’s water more efficiently.   

Thermostat and Controls  

Like any system that provides you with home comfort, water heaters do have features and components that ensure your comfort and safety. A common component that is similar between your typical HVAC system and a water heater is a thermostat. The thermostat for a water heater serves the same purpose as a thermostat for your HVAC systems. The main function is just general temperature management.   

Dip Tube  

The dip tube carries cold water to the bottom of the tank, where it’s isolated and heated before mixing with the rest of the hot water located at the top of the tank.

Cold Water Inlet Pipe  

The cold water inlet pipe supplies the hot water tank with fresh, cold water from the home’s main water supply, and also provides a shut off valve to stop water from filling the tank during maintenance, repairs, or emergencies.

Hot Water Outlet Pipe   

The hot water outlet pipe is what brings hot water from the top of the tank to your home’s plumbing system, where it is then distributed to the faucets, showers, and other fixtures throughout the home.  

Drain Valve  

The drain valve is an important component for regular water heater maintenance, helping to remove any buildup from your tank by draining a few gallons of water from your tank several times a year.

Remember the following steps when utilizing your drain valve for maintenance:  

  1. Turn Off the Water Heater: electric water heaters can be turned off at the circuit breaker; gas water heaters can be turned off by turning the thermostat to the “pilot” setting, and/or shutting off the gas supply.  
  2. Shut Off the Cold Water Supply: this can be done by locating the cold water inlet valve at the top of the water heater. Turn it off to prevent additional cold water from entering.  
  3. Attach a Hose to the Drain Valve: you can attach a garden hose to the drain valve (typically located near the bottom of the tank). Make sure the hose is securely attached to prevent leaks.  
  4. Direct the Hose to a Safe Draining Location: place the opposite end of the hose in a suitable drainage location. This can include a floor drain, an outdoor area, or a large bucket.  
  5. Open the Drain Valve: slowly open the drain valve by turning it counterclockwise and allowing the water to flow out of the tank through the hose.  
  6. Open a Hot Water Faucet: look for a hot water faucet closest to the water heater and open it. This will allow air to enter the tank, facilitating the draining process by preventing a vacuum.  

Anode Rod  

Extending and maintaining the life of your water heater’s tank is important and will help maximize your home’s comfort, and an important component that helps do this is the anode rod. The anode rod is a steel wire, typically wrapped with aluminum, aluminum/zinc alloy, or magnesium, running through the middle of your tank. The anode rod prevents corrosion within your water heater by attracting sediment, minerals, and other corrosive elements to the rod rather than eating away at the water tank.   

Temperature & Pressure Relief Valve (T&P Valve)  

All hot water heaters are equipped with a temperature-pressure relief valve, an important safety feature designed to prevent the tank from overpressure and overheating. It prevents your tank from exploding if the internal pressure exceeds a preset limit by causing the valve to open, release water, and reduce the pressure. When the pressure drops to a safe level, the valve closes.  

Gas Hot Water Heaters  

Gas water heater diagram

Gas hot water heaters are the most common type of water heater. They produce hot water quickly and gas is a significantly cheaper source of fuel than electricity. There are two types of gas that can power these units, natural gas and propane. Both varieties have a number of parts in common, but they are not the same. It’s also important to know which model you have, like a power vent water heater or a standard atmospheric water heater, as these all have their own unique parts.

Gas Burner and Burner Control Assembly  

The gas burner is the component responsible for generating the heat necessary to warm the water in the tank. The burner combusts natural gas or propane, which then creates a flame that heats the water. This process takes place in the combustion chamber located at the bottom of the water heater tank. The heat is then transferred to the water in the tank through the tank’s walls.   

Pilot Light and Burner Head

Two important components make up the burner. The burner head and the pilot light/ignition system play important roles within the burner. The burner head is the part where gas mixes with air, igniting and producing the flame. The pilot light or ignition system is what is used to ignite the burner.   


To prioritize safety, a thermocouple is an important safety device in gas water heaters. This temperature sensor measures the temperature within the tank by creating an electric current. This occurs when the contact end is either heated and/or cooled. The thermocouple needs to be tested and replaced if the pilot light frequently goes out, or if the burner fails to ignite.   


During combustion within a gas water heater, toxic fumes may be produced. Your gas water heater must have correct venting to safely manage the toxic fumes. Proper venting ensures that any harmful gases (e.g. carbon monoxide) are expelled from the home. Venting is important for several reasons; specifically when improving health and safety, efficiency, and performance, and it ensures that the system is compliant with codes and standards.  

Flue Baffle

The flue baffle is the part of a water heater directs toxic exhaust fumes toward the unit’s exhaust vents so they can be expelled.

Power Vent/Blower Assembly  

Another component that aids in proper venting is the power vent. Also known as the blower assembly, this compenet is designed to enhance the venting process by actively expelling toxic gases through a horizontal or vertical vent pipe.   

Electric Hot Water Heaters  

Electric hot water heater parts diagram

Electric Heating Elements  

In a standard electric water heater, there are typically two heating elements – one heating element is found at the top of the tank, and the second is typically found at the bottom. The upper element is activated first, heating the upper portion of the tank and ensuring that hot water is available quickly. The lower element is activated when the upper element reaches the set temperature, and it then heats the lower and remaining portion of water at the bottom.   

Circuit Breakers/Electrical Supply  

Circuit Breakers are essential safety devices in the electrical system of a home. The circuit breaker protects your electric hot water heater from damage caused by overcurrent, short circuits, and other electrical faults. When choosing the right circuit breaker for your water heater, you can look at two different things. One is the breaker size, which is looking at the voltage and amperage rating of your unit. The second is the overall compatibility between the circuit breaker and your hot water heater. It is important to look at wire size and panel compatibility when determining the compatibility between the your unit and the circuit breaker.  

Thermal Cut-Off Switch  

The thermal cut-off switch’s purpose is to keep your home safe and comfortable by monitoring the heat level of your system. In water heaters, a thermal cut-off switch will disrupt the power to the appliance’s heating mechanism if the tank ends up overheating. The typical temperature that triggers the switch is around 170 degrees Fahrenheit.  

Tankless Water Heaters

tankless water heater parts diagram

Tankless water heaters are the latest in water heating technology. These systems are quickly growing in popularity and have several unique components to be aware of.

Flow Sensor

A tankless hot water heater flow sensor measures the water flow coming into the unit, usually requiring a minimum water flow level before producing hot water.

Control Panel

Acting on a signal from the flow sensor, the tankless control panel turns on the hear source and lets you adjust the water temperature. Some brands even give you advanced programming and diagnostic error tools and can even be monitored and controlled by Wi-Fi!


What size water heater do I need?  

The most common water heater tank sizes are 40, 50, and 55 gallons. When determining which size water heater is best for you, it is important to analyze two things: the size of your family and the number of bathrooms. You want to ensure that the unit will be able to efficiently heat the water needed for your household.     

How does the location of the water heater affect its efficiency?  

The water heater’s location can determine how long the hot water takes to travel to the fixtures. Fixtures that are farthest away will not receive hot water as quickly as the fixtures closest to the tank will.   

What’s the average lifespan of a water heater?  

The lifespan of a water heater depends on the type, build quality, level of maintenance, and water quality. Similar to HVAC systems, a water heater’s lifespan can generally range from 8 to 15 years. Routine maintenance can give your water heater a longer life.   

How long does it take for a hot water tank to recover?  

The recovery rate for a water heater depends on the type of system. Gas water heaters take between 60-70 minutes to recover. Electric water heaters take around 120 minutes to fully recover.   

How does a tankless water heater work?  

Tankless water heaters are “on-demand” water heaters.This means that they only provide hot water when needed and do not use a tank for storage.   


Knowing and understanding your water heater can aid you in many ways. Knowing the components that make up your water heater will allow you to look out for any signs of dysfunction, which could then lead to safety issues. Understanding the parts of your water heater will also allow you to stay on top of your maintenance, increasing the efficiency of your system. There are a lot of components to remember and keep track of, so sometimes it is necessary to seek professional help!  

Contact Logan Services Today!

Our plumbing department is always ready to help customers with any plumbing and/or water heater needs! Regular maintenance and professional inspections will allow your home’s plumbing system to run at its fullest potential, ultimately increasing your home’s comfort. If you notice that your system is overheating, leaking, or not even heating at all, it may be time to receive a professional inspection. The team here at Logan Services is always ready to help.  Contact us today for a free estimate!

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