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Water Heater Parts – Get To Know Your Heater

Note: This post may contain affiliate links. This means that at no cost to you, we may receive a small commission for made purchases.

An appliance that breaks all social barriers and clarifies its omnipresence is a water heater. Very rarely will you find a household devoid of a water heater.

It has become a simple necessity today. But, do you know how your heater works? Do you know what each part does? Read on to find out.

Here, we will try to explain the functions of each part that makes up a gas or electric water heater (see also our step-by-step electric water heater installation guide).

Storage Water Tank

storage tank

A storage water tank is a crucial part of most gas-powered hot water systems. These heaters use a storage tank to maximize water heating capacity and offer instantaneous hot water at a moment’s notice.

A storage water tank attached to a water heater system can store approximately 60 liters of hot water for a long time, compared to the 5-6 liters offered by any other instant water heater system. You can barely get a bucket full of hot water from instant water heaters.

However, a storage tank water heater can store vast amounts of hot water. Also, a storage tank water heater can be powered by most fuels like electricity, propane, or fuel oil. However, the most common source of heat is natural gas.

Gas Valve

gas valve

A gas valve is another vital organ of every water heater system. It is responsible for allowing the flow of heat-inducing fuels into the heater’s body.

Upon opening the valve of a gas-powered water heater, the gas will enter the ‘pilot,’ where it will ignite and produce heat. Generally, two probes are sticking out of the valve body. The shorter probe is a safety device. It is designed to prevent any hazards from occurring due to temperatures getting out of control.

The gas valve is the gateway that you have to open to get hot water from your heater. It generally has a knob and a pilot button to handle and toggle for hot water.

Heating Elements

Copper Tubular Heating Element for Electric Water Heater, Electric Water Boiler

Every water heater has heating elements present in it. These are the heater system parts that make physical contact with the water and heat it up in the end.

When water enters a heating system, it is stored inside a container for a few minutes. Here, a specific tool, which can have various shapes and designs, contacts the water. That tool also heats up, consequently giving you hot water.

The heating elements can be rods dipped in the storage tank or the cylindrical lining inside the tank itself. They are generally made of metals since metals are good conductors of heat. Most commonly, electricity provides warmth to the heating elements, but other fuel sources can also do the job.

Anode Rod (Sacrificial Rod)

An Anode Rod is a coil of steel wire with magnesium, aluminum, or zinc wrapped around it. Its purpose is to protect the metal sheet lining on the inside of your water heater from rusting, or worse, exploding.

Both these debacles can happen if the heater is not used correctly for long periods of time. The anode rod also needs to be cleaned and replaced frequently. Since its function is to protect another part of the heater, it is also known as the sacrificial rod.

An anode rod essentially dissolves into the water. So, it would be best if you had it checked or replaced every two years. The composition of the anode rod can vary according to the water that is available in your home.

For hard water, i.e., water with a high pH, an aluminum anode rod is used. On the other hand, magnesium anode rods are used when the water pH is low.

Venting or Flue Pipes

ventilation pipes

A water heater system uses fuel of some kind to generate heat. Once the heat is generated, there is a systematic release of multiple exhaust gases.

These gases need to be released out into the atmosphere as fast as possible. A water heater system uses venting (see also ‘What Is A Direct Vent Water Heater?‘) or flue pipes – essentially, chimneys of some kind – to facilitate the transfer of exhaust gases outside.

Known by a variety of names – vents, ducts, pipes, chimneys, flues, etc. – the exhaust system in water heaters is made up of metal or plastic, depending on the usage. If very hot gases are going to be moved outdoors from the vents, then it is viable to use metal pipes instead of plastic.

Keeping exhaust gases inside the heater is risky business. These gases can cause the pressure inside the storage tank to increase, leading to some malfunction, or worse, an explosion. Exhaust gases need an exit, and the venting system provides just that.

There are a few types of venting systems – direct venting, power venting, atmospheric venting, etc. These systems offer the same functions with the help of different mechanisms.


water heater blowers

Blowers are a commonly used part of power vent water heaters. Essentially, they constitute an ingredient of the venting system we discussed above.

In a power vent water heater, the vents are organized horizontally. As a result, the hot exhaust gases, which are bound to rise upwards, cannot move ahead.

Therefore, these horizontal vents have a fan installed in the system to propel the hot gases out. These fans are called Blowers. They are powered by electricity and are needed when the vents or ducts cannot push the hot exhaust gases out.

Dip Tube

The function of a dip tube in a water heater is simple. It is built to direct cold water to the bottom of the tank for heating. Cold water generally enters the storage tank from the top, where it merges with the already warm water.

However, for the cold water to become warm, it has to reach the bottom of the tank, where the heating elements can warm it up. Therefore, the dip tube runs this mission of moving cold water downwards.

As the name suggests, the dip tube is a long tube running from the top of the container to almost the bottom. The opening at the base ensures that incoming cold water directly enters the bottom of the heating container.

Gas Burner Assembly

Gas Burner Assembly

The gas burner assembly is responsible for burning the gas or fuel in the heater. It is controlled by a regulator on the outside of the heater, along with a thermostat.

The burner assembly ensures that the fuel is converted to heat energy, allowing the water to get warm. Gas burner assemblies are found only in gas burners, generating a flame at the bottom of the storage tank.

They are parallelly related to heating elements in electric heaters because they have the same function.

ECO (Emergency Cut Off)


Every water heater has an ECO (Emergency Cut Off) mechanism installed. It is this system that prevents all kinds of mishaps in a water heater system. When there is the slightest notice of overheating in the tank, the ECO will spring into action and shut down the heater entirely.

If you find out that your heater has been switched on for a few hours by mistake, you can easily trigger the ECO by pressing an emergency button on the body of the heater. To reiterate, all heaters have the ECO in place to prevent any explosions due to overheating or circuit failure.

TCO (Thermal Cut Off)

The Thermal Cut Off switch is also present on every water heater, and it protects our appliance from having to undergo costly repairs. It prevents the temperature inside the tank from going beyond 180 degrees.

If the temperature does go above the specified high limit, the ECO triggers its functions and shuts down the heater entirely. However, that could mean that crucial parts of the heater may be damaged. Therefore, the TCO kicks into place to prevent unnecessarily high temperatures from damaging the thermostat valve on your heater.


water heater thermostat

The thermostat is an integral part of the water heater. It reads the temperature in the tank and accordingly adjusts the heating devices to provide water of the temperature you desire.

Once you set a temperature on the thermostat, it will give just enough heat to the water to get the temperature right. If the water is getting colder than you want, the thermostat will add warmth to the mix.

On the other hand, it will also take off the heat if the water is becoming too hot. Ideally, a thermostat saves you from using unnecessary heat and has the potential to cut down your electricity bills.

Flame Arrester

As the name suggests, a flame arrester in a water heater prevents a flame from burning inside the system. It is essentially a filter that allows hot gases to pass through but dials down on any flame that it might encounter.

It is a passive device designed to prevent a flame from generating an explosion. The vapors generated from hot gases are flammable and can have a dastardly effect on some parts of your heater. The flame arrester puts an end to the possibility of a flame.

TPR Valve

Temperature pressure valve

The Temperature Pressure Relief Valve in your heater is responsible for increasing the outflow of water from the tank to decrease the pressure inside. Due to constant heat and the release of hot exhaust gases, the pressure inside the water heater body may rise to dangerous levels.

The TPR valve takes care of such situations by decreasing the pressure inside and preventing any mishap. TPR valves automatically release water inside the tank, and they are present in most kinds of heating machines.

Drain valve

screw loose to drain heater tank

If you have ever wondered what the first step to removing, repairing, or shifting your heater was, then the drain valve is your answer. The drain valve essentially drains all the contents of your heater tank, allowing you to safely remove the tank, clean it, repair it, etc.

While replacing essential parts of the heating system, the first step is to open the drain valve and allow the tank to become empty. Opening the drain valve is a standard precautionary servicing procedure that drains all sediments that may have built up inside the tank.

Air Pressure Switch

The Air Pressure Switch on a water heater is present on all power vent variants, and it checks whether all products of combustion have been emptied or not. Essentially, it keeps the venting clean and free of any residue.

Gaseous residue in a power vent water heater is an unsafe phenomenon and needs to be cleaned immediately. Therefore, an air pressure switch declutters any exhaust particles that may have been left in the vents and cleans them up.


Most water heater systems are insulated when they are sold. However, research says that adding insulation to heaters in constricted spaces can increase their efficiency.

If your heater is located in an area devoid of air conditioning or ventilation, you do not want it to get extra hot. Insinuating the outside of the heater is a tricky task, but you can do it so that heat energy dissipates efficiently.

The insulation inside a heater is present between the metal cylinder and the tank, so you cannot see it. However, you can check the label for more details.

Water Heater Timers

Gray Box Timer

Water Heater Timers tell the home occupants when the heater will function. Homeowners can program the timers – like an alarm – so that the water heater works automatically at that stipulated time.

If you have a relatively stable schedule, you can use a timer for your water heater and ensure that you get a hot bath drawn for you every day after work, for example.

Moreover, if you know that the house will be unoccupied for long periods, you can use the timers to dial down the heater and bring it back to life when you are coming back.

Mixing valve

mixing valve

A mixing valve has a simple job – holding the water inside the tank at a higher temperature and mixing cold water with it to increase the capacity of the tank.

Storing hot water at a higher-than-usual temperature can prevent the growth of bacteria inside the tank. However, the increased temperature is not enough to harm any devices inside the water heater.

Moreover, opening the mixing valve will mix cold water with the already existing hot water. It will create more hot water in your heater.

Recirculating Pump

A recirculating pump has no mystery around it and stays true to its name. It is a pump, generally installed in electric water heaters, whose function is to take unused hot water back into the water heater tank.

The returned water can serve as an emergency or instantaneous hot water for you. If you ever need hot water on demand, then this recirculating pump does the job for you. The unused hot water moves back into the heater from a separate dedicated pipe or through the cold water channel itself.

Expansion tank

Expansion tanks

An expansion is a vital force inside the working of a water heater. It is a tank designed to account for the expansion of water as it turns hot.

As the water gets warm, it expands, and the pressure inside the tank rises. An expansion tank counters these movements and prevents pressure from building inside the tank.

Thermal expansion of water can raise the pressure through the roof and cause damage to the plumbing valves, joints in pipes, or even the water heater itself. Thermal expansion always occurs in water heaters. Therefore, expansion tanks are a necessity.


These are a few of the most important parts of water heaters that you can commonly observe. They are essential in their functions, and the heater only works when they all work well.

author avatar
Charlie Hardcastle


On Key

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