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What Size Expansion Tank Do I Need? (Answered And Explained)

We all know the bigger the expansion tank, the better it is. However, it also gets costlier if you go too big. So, you want to hit that sweet spot.

Now the question is, what size expansion tank do I need? Simply put, the size of your expansion tank depends on the heater size. To accommodate a big heater, you must buy a big expansion tank. However, it’s good to select a tank that is at least 1 size larger than your water heater.

If you are asking for a rule of thumb for the size of expansion tanks, we have all the answers prepared for you. Without further ado, just go over the details thoroughly so that you don’t miss out on anything.

What Size Expansion Tank Do I Need

What Size Expansion Tank Do I Need?

If you get the sizing wrong, it’ll cause many problems down the road, and it’ll cost you too much trouble.

So, it’s better to get things right from the very beginning. However, the great news is that you can go for a slightly bigger expansion tank, and it’ll work safely but cost you some extra bucks.

But going below the recommended size will cause issues and mess with the machine’s durability. You can see how getting the right-sized expansion tank can save you from issues and help save money as well.

Below, we have a sizing chart prepared for you that you can use to figure out which size of expansion tank you need for your water heater.

Remember, the temperature should be set to 150 degrees to match the following chart. Without any delay, let’s check the expansion tank sizing chart right now.

Expansion Tank Sizing Chart:

Capacity of the Water Heaterpsi (Supply Pressure)Size of the Expansion Tank
40 to 60 Gallon40-50 psi2 Gallon
40 to 60 Gallon60-80 psi3.2 Gallon
80 Gallon40 psi2 Gallon
80 Gallon50-60 psi3.2 Gallon
80 Gallon80 psi4.4 Gallon

Why Does The Size Of An Expansion Tank Matter?

Now that you know what expansion tank is perfect for your water heater, it’s time to discuss why it’s important to get the sizing right in the first place.

You can get away with an oversized expansion tank as it doesn’t cause excess pressure. But, when the size is smaller than ideal, that creates a lot of problems.

First of all, a small expansion tank can cause too much pressure on the system. It also causes the hot water to expand out of control and ultimately results in a relief valve discharge.

As a result, it can ruin the entire water heating machine with the excessive expansion tank’s air pressure. So, you might have to repair the whole thing to make it work again. It is not only costly but also takes too much effort.

Hence, it’s best to fix the issue from the very beginning so that you don’t have to waste your time, energy, and money on repairing it later on.

Also, as I said earlier, bigger expansion tanks are pricier, and you don’t want to get an oversized tank as it won’t do you any good.

So, by getting the right-sized tank, you’ll get the best deal for your money as well as the perfect performance. Mind you, you should never pick any random-sized expansion tank and install it on your water heater.

Take a few moments to understand your system better and get the perfect expansion size. It’ll make your life so much easier in the future for sure.

multi size expansion tank image

Things to Follow When Selecting Expansion Tank Size

As you have the sizing chart now, you can pick the right expansion tank for your residential heating system easily.

However, it’s not the best idea to pick the size if you don’t know what the labels mean and what to consider before choosing the size of the expansion tank.

Luckily, it’s not that complicated as you only have to worry about 2 things. If you get the hang of these two factors, you’ll be able to easily pick the right-sized expansion tank for any water heater system.

Below, let’s discuss these 2 factors that you need to know about in detail.

The capacity of the Water Heater

This is the first thing you need to check before you try to pick an expansion tank for your water heater.

It’s very easy to find, and manufacturers add it to their heaters for the ease of their users. You can check the factory label of the water heater, and it’ll have the capacity labeled there.

The capacity of water heaters is measured in gallons. So, you might find something like 40 gallons, 50 gallons, 55 gallons, etc., on the factory label.

That is the capacity of your water heater, and it’s the most important piece of information you need to pick the right expansion tank size for it.

Supply Pressure (psi)

Next up, you just need to find out the pressure of your water heater. That is labeled as “psi”, and it’s the 2nd and last piece of information you need to find out the recommended expansion tank size for your water heater.

For instance, a heater can have 50 psi, 60 psi, etc., on the factory label. You need to check out this information and choose the expansion tank accordingly.

Final Thoughts

We just went through an in-depth guide on getting the expansion tank sizing formula down. Hopefully, now you can choose the right expansion tank for your water heater.

Make sure that you consider all the factors carefully, as it’ll help to save you a lot of trouble in the long run. Not to mention, you’ll get the best performance from the water heater as well.

So, take a little extra effort and get the size of the water heater expansion tank correctly. It’ll be worthwhile, and you should definitely not neglect that.