If you’re here to find out what a water heater expansion tank is used for and whether you need one or not, you’re in the right place. In this article, I’ll explain what the main purpose of a water heater expansion tank is and from that, you should be able to figure out if you should invest in one.
Water heater expansion tanks are installed on closed plumbing systems also known as a closed loop system. When the water heater heats water, it expands and pressured water flows into the expansion tank. This is necessary – as with closed plumbing systems, the expanding water has nowhere to go (unless there’s an expansion tank) and will cause damage to the heater and or other plumbing fixtures.
So, if you’re ready to learn more, then please read onward…
Why Would You Need a Water Heater Expansion Tank?
In some cities, it’s required that water systems (the water lines in your home or a business) have backwater or check valves installed on water lines. This is to prevent the water that has entered your home’s water system from leaching back into the city water supply.
If there’s contamination in your homes water lines, it wouldn’t get into the city supply when a check valve is installed.
Is an Expansion Tank Necessary on a Water Heater?
An expansion tank for a water heater is only necessary when your home’s plumbing system is a closed loop – meaning there’s a check valve on the water line that supplies your home with water.
If this is the case, then having an expansion tank will help to prevent damage to plumbing fixtures and your water heater. It’ll also help extend those fixtures’ lives as the pressure from a closed system can weaken and damage your plumbing.
However, you could go without an expansion tank and be just fine for some time. I don’t think I would take that chance, though.
Is an Expansion Tank Required by Code?
In some municipalities in North America, expansion tanks are required by code.
If you have a closed plumbing system, then you have a check valve installed shortly after your water lines enter your home. This is to protect the water supply from being contaminated by water leaching back into the municipality’s supply lines. An expansion tank would then be required by code to protect you and your family.
How does a Hot Water Heater Expansion Tank Work?
Hot water heater expansion tank is filled with air. When water from the heater expands, it moves into the expansion tank compressing the air.
You might think that air can’t be compressed but surprisingly, it can. Of course, it’ll only compress so far so having the proper size expansion tank for your sized heater is imperative.
When the hot water moves from the heater to the expansion tank, think of the air inside as a coiled spring. The water pushes on the air (spring) and compresses it. When the water cools and flows back into the heater, the air can then expand.
Is an Expansion Tank Necessary on a Water Heater?
An expansion tank isn’t necessary on a plumbing system that isn’t a closed system. If it’s a closed system, you should have an expansion tank.
You could take the chance and not install one, but you’ll most likely find out quickly that you need it.
How Often Should an Expansion Tank be Replaced?
An expansion tank can last upwards of 10 to 12 years.
It’ll depend on the pressure of your water system and the pressure of the air in the tank. If you can set the plumbing system’s water pressure to match the expansion tank’s air pressure, the unit will last a lot longer.
When Should an Expansion Tank be Installed?
If it’s code for you to have an expansion tank, then it should be installed when the water heater is installed. If you’re adding one just to improve the life of your water heater and plumbing fixtures, then whenever you can install one is up to you.
How Big Should an Expansion Tank be?
For an average sized 50-gallon water heater, a 2-gallon expansion tank should suffice. A 60-gallon water heater should have at least a 3-gallon expansion tank and an 80-gallon water heater should have at minimum a 4-gallon expansion tank.
How Much Does an Expansion Tank Cost?
The cost of an expansion tank will differ from city to city around the country however, on Amazon you can purchase them for $50 for a 2-gallon. The bigger tanks cost more money as you would expect.
Check out these expansion tanks on Amazon.
How Do You Know if Your Expansion Tank is Working?
The best way to check if an expansion tank is working is to look for clues as to it not working or failing. Make sense? Let me explain.
Because these tanks are filled with air, if you knock on it with a wrench or hammer, the sound should be of a hollow nature. If it makes a thud (or dead) sound, then it could be filled with water and might be faulty.
This issue with this is if the tank sounded like it might have water it could just be the hot water expanding into the tank. That’s why you have the expansion tank so how can that be a problem?
The expansion tank shouldn’t have water in it all the time. It’s to help relieve a small amount of pressure produced when the water in the heater is heated up. So, it should never sit in the tank too long.
If you found that the tank sounded dead (or full) when you banged on it, you should wait an hour or so and check again. If the sound is now a hollow type of sound, then everything should be working properly.
If it still sounds like there’s water in it continually, then you have a problem and it needs to be fixed. If you’re not a handy person, you should call a plumber.
Final Thoughts
To wrap up this post, I want to point out that if your plumbing water supply line coming into your home from the city or town has a backwater or check valve, its a great indication you should have an expansion tank installed.
Of course, the easiest thing to do if you’re still not sure whether you need one or not is to contact your town office or doing a quick search on Google might also help you with that information.
You could install a water heater expansion tank yourself if you’re a handy person but if you question any part of this article, then there’s a good chance you should reach out to a professional.
Installing an expansion tank can be done by either a plumber or a handyman.
Thanks for reading and good luck!
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