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Expansion Tank Installation

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

Everyone knows that water heaters consume and generate a lot of energy. So, it should not be a surprise as you hear about the potential issues even the slightest pressure change can make.

The same is the case with water expansion, which happens when the water temperature goes beyond a limit.

Therefore, many places may ask you to have an expansion tank along with your water heater unit. More importantly, experts often ask you to add it to the package for enhanced safety.

Either way, expansion tanks for water heaters are pretty popular in the market right now. However, we cannot say the same about how much users know about the expansion tanks.

Most importantly, expansion tank installation remains more of a mystery for most people. Some people say that it is only for experts, while others claim that DIYers can do it without breaking a sweat.

If you ask us, the truth stays in between these points. But, before installing an expansion tank next to a water heating system, you have to understand a few things about expansion tanks and how they work.

We have prepared this article as a one-stop place to answer all your questions. There is also a step-by-step guide to expansion tank installation.

What Is an Expansion Tank?

about water heater expansion tank

An expansion tank is a simple safety device that prevents water expansion from damaging your water heater or plumbing system.

An expansion tank is technically an additional tank that you can set up next to the water heater. Before we talk about how an expansion tank works, we have to talk about water expansion and water pressure.

As you may know, your home and plumbing appliances need to have stable water pressure. If the pressure decreases, you will not receive enough water from the outlets.

On the other hand, if the pressure exceeds the recommended levels, there could be leaks and other issues. Water expansion is one of the usual reasons for high water pressure. It happens when the water pressure increases due to the expansion.

And the water gets expanded when it is subjected to heat. That is, when your water heater takes up cold water from the supply and heats it, the water will expand by up to 2% or more depending on the heat.

The problem has to deal with this point: where does this expanded space go? Usually, the expanded water could go back to the source, but most plumbing systems attach a system to prevent back-flow.

That is, the expanded water would not be able to go back to the supply. As a result, the expanded water may move to the water heater tank, pipes, fixtures, and other components in the plumbing system. Because these objects receive too much pressure, there could be leaks or other problems.

Well, an expansion tank solves this issue by introducing extra space. An expansion tank is a container that is split into two sections by a rubber diaphragm. One of these sections will accept expanded water from the water heater tank.

The other section will increase its pressure as the first one accepts the water. The water expanded because of the extra space and the pressure change system because the heating process has an area to go. It can essentially prevent leaks and other damages.

Why Having One Expansion Tank Is Important?

benefits of expansion tanks

Are you still wondering why you should get an expansion tank? Here is a list of the significant benefits you may want to know.

  • As we mentioned earlier, a water expansion tank can prevent extra pressure from damaging the water heater, your plumbing accessories, or the outlets. Because it takes care of the additional pressure that may occur due to thermal expansion, you do not have to worry about the heat damaging any of your equipment.
  • You may already know that high pressure is not suitable for the health and durability of appliances. So, by adding a water expansion tank to the package, you can increase the longevity of your devices, especially the ones taking hot water from the heater. You can also decrease the frequency of parts replacement.
  • In many areas in the United States, having an expansion tank is a necessity. Since we cannot predict the problems that extra pressure may cause, especially with heavy-duty water heaters, authorities have made expansion tanks mandatory. Of course, it has been done to increase the longevity and durability of the plumbing systems.
  • From a usability point of view, expansion tanks can increase the stability of water pressure across the household. Even if there are problems with the water supply, the tank will take care of them. So, you can have a convenient water pressure of 50psi at all times. Rest assured, even when you turn off everything, you do not have to worry.

As you can see, the advantages of having an expansion tank are significant. We should also keep in mind that water expansion tanks are not that expensive.

Because the system is simple, the manufacturing costs of these devices are low. When you spend around a thousand dollars on a heavy-duty water heater, adding a good expansion tank to the package would not be a problem.

In short, financial constraints would not stop you from getting one of these devices. The next big thing is the installation process, which we will cover in a bit. Spoiler alert, it would not be a problem, either.

How To Install Expansion Tank

expansion tank istallation

Installing an expansion tank is not rocket science, but it is no child’s play either. Therefore, you must be very careful while setting up an expansion tank.

In the end, if the setup has some leaking issues, you will defeat the purpose of the tank itself. If you are confused about any steps that we have mentioned below, you have two options.

One, you can ask the community on the web or go through the documentation. Two, you can stop the job right away and hire a professional. A half-baked installation of an expansion tank will do more harm than good.

First, we will look at the tools and other equipment you need.

Tools and Equipment Required

  • The brand-new thermal expansion tank
  • Pipe-sealing tape
  • Pipe wrench
  • Dielectric water heater nipple
  • ¾-inch copper female-threaded unions
  • ¾-inch copper tee-fitting
  • ¾-inch copper pipe

In addition to these, you may have to get other equipment for plumbing and soldering. You may also want to add some extra copper fittings as required.

As you may have noticed, many of these elements can increase the overall safety of the water heater setup. Therefore, you may have to increase the number by a long shot.

Step-By-Step Guide To Installing Expansion Tank

tank installation steps

You have to follow the steps we have listed in the same order to install an extension tank properly. It would help if you kept in mind that some steps may vary depending on the expansion tank model.

Still, the steps are great to get the basics right. We highly recommend going through the user/installation manual that you got with the expansion tank.

The manufacturer will mention the same in the support literature if the product has unique features or design differences. Depending on these instructions, you may have to add a few materials or accessories to the package. Alternatively, you may have to use some more pipe-sealing tape.

By the way, you should also check if your expansion tank works with the water heater you have at the home or office space. You will have to choose an expansion tank that can provide enough space for the expanded air, you know.

If you are concerned about this step, you should check with the plumber to learn more. Once you have confirmed the compatibility, getting the expansion tank will be one of the most effective purchases you can make.

  1. As the first step, you have to turn off the water heater and disconnect the plug. You do not want any electrical interference when you are setting up the expansion tank. We also suggest turning off the supply to your house. If you think the water pressure on faucets is too high, you can drain the water already in them.
  2. You have to connect a dielectric union to the port that cold water uses for entry. You may have to use multiple layers of pipe-sealing tape to ensure that the union is appropriately attached. You do not want any leaks happening at this point, trust us. After this, you can thread the union into the inlet for cold water.
  3. In this step, you have to attach a copper adaptor to the system. Once again, you can make use of the pipe-sealing tape. Once you have done that, you can use the pile wrench to thread the female-threaded copper adaptor.
  4. Once you have done these, you have to install the tee fitting. Make sure that you leave enough space between the water heater tank and the tee-fitting. It is done so that there is enough clearance for the expanded water to move. By the way, if you have some experience with plumbing, you may use different wiring methods. For instance, some plumbers use sweat-soldering techniques, while some others may use the push-fit connection.
  5. Now that you have set up the containers, you can attach the expansion tank. You have to locate the threaded adaptor on the horizontal pipe and screw it in the tank properly. Unlike other equipment, water expansion tanks must not be over-tightened. Applying too much pressure on the horizontal pipe may cause further leaks in the system. Therefore, we recommend using your hand to tighten the screws instead of a professional wrench.
  6. In this last step of the installation, you have to connect the outlets to the expansion tank. You have the option to choose between multiple methods to ensure the connection. For instance, you can use a copper flex line to connect the outlet to the expansion tank. Alternatively, you can use other fittings that you are familiar with. With steps, you can conclude the installation process.

Given that you have completed the installation process, we can now move to quality testing. Before testing for pressure and everything, you should do a thorough check for leaks.

If you find any leak, you can tighten the area or use pipe-sealing tape to avoid the leak. Once you have ensured that the new system does not leak, you can turn on the entire system and check for pressure.

We recommend multiple instances of quality check, especially if you leave the system in a difficult-to-access region.

Helpful Tips During Installation

expansion tank installation place

  1. You do not have to place the expansion tank so close to the water heater. So, if your space does not have constraints, you should keep a considerable amount of difference between the tank and the heater. It will increase the overall security of the system.
  2. There is no perfect angle for setting up an expansion tank, either. Many makers would ask you to go for the vertical position, but upright angles would not be a problem. You can also use the additional mounts that came with the package.
  3. You can indeed get a water expansion tank for as low as $50. However, it does not mean you have to stick to that budget. Instead, it would be best if you tried to get the best tank for your needs. After all, you do not want to upgrade this equipment every year, do you?
  4. Unfortunately, an expansion tank is not install-and-forget equipment. If you make considerable changes to the plumbing system in your house, you should check the expansion tank for safety and maintenance. One of the common problems is the rupture of the rubber diaphragm, which can cause problems like diffusion.

We hope these tips help you in installing and operating the tank.


As you can see, expansion tank installation is not your happy-go-lucky DIY project. 

But, with the right tools and guides, the process would not be Herculean either.

Therefore, make sure you go through all possible literature before installing the expansion tank you bought.

author avatar
Charlie Hardcastle


On Key

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