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Does My Water Heater Need an Expansion Tank?

Residential Hot Water Heater Expansion Tank.

Do you know why you need an expansion tank for your water heater? If not, read through to understand why. The average lifespan of most water heaters is 10 years.

However, the number can reduce due to leaks and bursts for various reasons.

Understanding the benefits of an expansion tank and how it works is essential. It is the first step to understanding the power of this device and how to utilize it.

If you have a water heater and think you need an expansion tank. It would be best if you answered some questions to find the answers to your concerns.


You could be wondering if you need a water heater expansion tank, but there is no straight answer unless you answer two questions:

  1. What is the type of your water heater? If you have a tankless water heater, you do not require an expansion tank because it has no storage. You must answer the next question if you have a traditional water heater.
  2. What is the type of your loop water supply system? If you have an open-loop water supply system, you do not need to find an expansion tank because water can go back to the source. Still, if you have a closed-loop water supply system, you should get an expansion tank because you get water from an outside source, and the water in your pipes cannot return to your provider’s water supply system.

An expansion tank is a very small component but very essential that protects your home from any harm. It absorbs excess pressure from various appliances and ensures they do not damage each other.

To ensure your water heater expansion tank, you must maintain it by pumping it once a year because the bottom half contains compressed air, which reduces over time. You can use a bicycle pump when the pressure is below 50 PSI.

Before installing an expansion tank, you must know the exact size you should get. You should consider two factors to determine the size of an expansion tank that you should buy. That is water heater capacity and household water pressure.

It is vital to update your home to current codes when major repairs, modifications, and replacements happen. Ensure your water heater complies with the current plumbing code of your state when repaired or replaced.

Determining if You Need an Expansion Tank

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The following two questions will help you know if you need a water heater expansion tank or not:

  1. The type of heater you have. If you have a tankless heater, you do not need to worry about it though it is dangerous because it has no storage tank. However, if you have a traditional water heater, proceed to the next question.
  2. What kind of loop water system do you have? If you have an open-loop water supply system, water can return to the source. In this case, you do not have to look for a plumber or an additional expansion tank. However, if your home has a closed-loop water source, you get water from your provider’s water systems. Therefore, you need an expansion tank because it has a one-way valve installed on the water supply, and the water from your plumbing system cannot return to the provider’s water systems.

What Is a Water Heater Expansion Tank?

Expansion Tanks In Boiler-Room

It is a small tank but very crucial that prevents excessive pressure from harming your house. When you heat it, it contracts with increased force due to thermal energy and its size before it releases extra strength back out when you need it when taking a shower.

It is a safety measure that protects you and all other home appliances from potential damage. It takes extra pressure from all the appliances in your home to ensure they continue operating without causing danger to one another.

An expansion tank provides insurance against ruptures, corrosion, and leaks caused by excess heat exposure.

It also prevents clogging caused by accumulated sediments in valves and pipes. However, this can be improper or tempered during installation or maintenance over time.

A water heater expansion tank is a practical lifesaver. Therefore, you should take it as a guardian angel for your water and plumbing leaks.

Ensure you have it all the time to prevent mentioned risks.

How Water Heater Expansion Tank Works

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You need a water heater expansion tank for any water installation, especially if you have more than one appliance that draws from the same hot water supply line.

Although tankless heaters are very popular nowadays, they are dangerous because they do not have a storage tank. Therefore, whenever a demand spike or several appliances start at once, leading to an excessive flow rate of hot water in the plumbing can lead to problems.

The expansion tank absorbs excess pressure ensuring everything runs smoothly without causing any damage to your appliances.

If you live in an area with cold winter, install an expansion tank on your system if you have a tankless water heater.

Whenever the temperature drops too low, the water in the pipes starts freezing, forming ice that expands and can cause damage to the plumbing, or the pipes can rupture.

An expansion tank helps prevent such incidences because it takes up some excess space. Therefore, the freezing process cannot cause much pressure on the system.

How To Maintain Water Heater Expansion Tank

Men Hands Screwing Valve With A Spanner

The bottom half of an expansion tank contains compressed air, but it can lose some pressure as time goes by. It has a Schrader valve similar to the one on the bicycle tires.

Check it annually with a gauge to see if it has sufficient charge. Pressurize it if it is less than 50 pounds per square inch using a bicycle bump.

Why You Need an Expansion Tank

Plumbing Service. Copper Pipeline Of A Heating System In Boiler Room.

Most water heaters have an expansion tank. However, if you got your water heater before 1986 or you are unsure, you can look for a qualified plumber to check it for you.

The expansion tank needs to be of an appropriate size to ensure a maximum flow of the plumbing at your home. It should be next to the pressure-reducing valve along the cold water line.

Bear in mind that an expansion tank is essential and can do so much, and in case of bursts or leakages anywhere in the system, you will not require extra pressure from the tank.

If you encounter problems, seek professional help to ensure everything works perfectly.

If you use a tankless water heater and live in a place that has very cold winters, ensure you install an expansion tank on your system to avoid damages that may occur due to freezing when the temperature drops too low because the tank takes up some spaces preventing the freezing from causing so much pressure on your system.

The Size of the Expansion Tank You Need

Blue Thermal Water Expansion Tank Connected To Copper Piping.

When you get a water heater expansion tank, you cannot think of its installation without determining the size you require. The size of your water heater determines the size of the expansion tank you need.

There is no one size fits all expansion tank. Therefore, if your water heater is large, so should the expansion tank. However, you must consider two factors:

  1. Household Water Pressure: It is measured as pounds per square inch which you can find on the water pressure gauge at your home.
  2. Water Heater Capacity: It is found on the label provided by your water heater manufacturer.

Once you find out the above two factors, you can find an expansion tank that suits them by consulting a professional plumber sizing a graph.

Benefits of an Expansion Tank

Expansion Tanks With Pressure Gauges In Boiler Room

There are various benefits of expansion tanks for your and your appliances:

  • Ensure the machines run smoothly without causing any damage.
  • Prevents corrosions, leaks, and ruptures caused by excessive high-pressure temperatures.
  • It is essential for tankless water heaters for individuals living in cold weather areas.
  • It ensures pipes and plumbing do not freeze and rupture in extremely cold weather.

The Lifespan of an Expansion Tank

New Gas Boiler, Heating System With Copper Pipes, Valves And Other Equipment In A Boiler Room Gas Heater System, Modern In New House White Wall.

Several variables make it hard to calculate the lifespan of an expansion tank:

  1. Skills of the technician who installs the tank.
  2. The quality of the tank.
  3. Proper inflation.
  4. Water quality.

All the above variables affect the duration your expansion tank will serve you. Some tanks can last for 2 years, while others last for more than 8 years.

When you buy a water heater expansion tank, ensure you seek professional assistance for installation and replace it a year after the expansion tank warranty expires because you can end up with countless water damage.

The warranty cannot help you out anymore once it expires.


You could be wondering if you need a water heater expansion tank, but you can not get a straight answer unless you provide details about your water heater.

An expansion tank is an essential component that protects your home from dangers because it absorbs excess pressure from all your appliances.

An expansion tank ensures appliances do not damage each other. Although the expansion tank is a tiny component, it plays a vital role in your home.

When installing a water heater expansion tank, do not just buy one because you must determine the size you should get. You can seek help from a certified plumber to decide your exact expansion tank size.

The lifespan of the water tank you buy depends on various factors. Ensure you replace it not more than a year after the expiry of its warranty.

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