Where are Thermal Expansion Tanks Installed: Illustrated Guide - Home Inspection Insider (2022)

Where are Thermal Expansion Tanks Installed: Illustrated Guide - Home Inspection Insider (1)

Even before we look at where expansion tanks are installed and whether it is on a hot or cold line, we need to understand what the tank involves. An expansion tank is a safety device installed on a heating system to protect fixtures and pipes in a plumbing system not fitted with a backflow preventer or check valve.

In most cases, most local plumbing codes must install an expansion tank when you install a new water heater on the municipal water supply.

Expansion tanks are installed on the cold water pipe above the water heater. Generally, expansion tanks are installed in an upright position. However, they can be installed inverted or on their side, provided it is strapped for support. A water heater expansion tank is a small air-filled tank that acts as an expansion chamber to control increased water volume created as water is heated and expands.

This article will explore where an expansion tank is installed and how to manage an installation by yourself.

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How an Expansion Tank Works

An expansion tank is required in certain circumstances and can help a water heater last longer. We all know that water expands when it’s heated. Without an expansion tank linked to the water heater, any closed plumbing system can undergo severe damage due to thermal expansion.

For instance, when you heat water from 50 to 120 degrees Fahrenheit, its volume rises by about 2%. If you have one in place, it offers space for expanding hot water, reducing excess pressure on the pipes, fixtures, and water tank.

Expansion tanks are essential in closed plumbing systems. Backflow valves or pressure-limiting valves prevent the expanding water from flowing back into the central water supply unit. It has two sections; the first one has an air chamber pressurized when the diaphragm expands, while the other section accepts expansion water when it heats.

Where are Thermal Expansion Tanks Installed: Illustrated Guide - Home Inspection Insider (2)

Expansion Tanks Might Be Mandatory

Installation of a water heater requires a plumbing permit. You get to learn about the requirements of an expansion tank when you’re applying for a plumbing permit. In most cases, though, you might be forced by your local authorities to install a water tank, where you have a water heater.

However, an expansion water tank isn’t necessary if your system doesn’t have any backflow or pressure limiting valves. If your system has those valves in place, it would be wise to install the tank even if your local code doesn’t make it mandatory.

Where to Install an Expansion Tank

Where would you install a new expansion tank? First, use a tee-fitting above the water heater on the cold water delivery pipe. The tank is usually positioned horizontally.

However, in cases where you have limited space, you can install the tank vertically. The plumbing fittings you’ll require for installation will depend on the types of pipes you have and the tank orientation.

Connections during installation are made using copper fittings and pipes. The expansion tank has a 3/4-inch fitting joined to the cold water pipe using a tee fitting and threaded or sweat-soldered or short-length pipes.

Supplies and Tools You Need During Installation

There are various supplies and tools that you must have ready while installing an expansion tank, as highlighted below:

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  • ¾-inch copper tee-fitting
  • Pipe-sealing tape
  • Thermal expansion tank
  • ¾-inch copper pipe
  • Copper flex pipes
  • Dielectric water heater nipple
  • A plumbing soldering equipment
  • Channel-lock pliers or pipe wrench
  • At least two ¾-inch female-threaded copper unions
  • Extra ¾-inch copper fitting

Preparations for Installing an Expansion Tank

If you already have an expansion tank and want to add another one on top, you must first drain water from the water heater. Before you start, you must ensure that you have enough space over the water heater to place the expansion tank.

If you are making a completely new installation, there is no need to drain anything. Therefore, it would be best to skip directly to the processes of installing the tank. First, let’s look at how you can prepare for installation by draining the tank:

  1. The first step is to turn off the mainline supply of water that connects directly to the cold water side of the heater.
  2. You can then join a hose on the drain valve below the heater and run it to the other end of the nearest drain.
  3. Release pressure from the water heater tank by opening the drain on the hot side of the closer faucet and the water heater. Don’t open the valve too fast or too much; this may lead to a slide from the drain.
  4. After draining for some minutes, open the T&P valve slightly to test the pressure. If there is no pressure, head to step 5. If you notice some pressure, wait for a few minutes and then repeat step 4.
  5. You can finally shut off the faucet and turn off your drain valve once you notice that there is no more pressure from the water heater.

Steps to Installing an Expansion Tank

After preparations, this is now the time to install. First, however, there are steps that you must follow if you want to be successful. Let’s look at these steps:

Make a Plan

Nothing successful starts without a plan. Even the most successful military expeditions begin with a plan on paper. For this project, you need a good plan to run a branch line off to the expansion tank from the hot water tank cold water application.

Please sketch the diagram. You can also obtain the right fittings that you will need to operate a line from the expansion tank up to the tee-fitting inserted in the cold water supply line. If you’re lucky, you might only require a single Tee-fitting and one fitting for the end of the expansion tank.

There usually is at least one elbow fitting required.

Choose Your Spot

The installation can be more straightforward if you have PEX lines in your apartment. If there are copper lines, everything is still doable but can be somehow complicated. The first step here is to decide the exact location where you would like to mount the expansion tank.

The expansion tank should be mounted above the water heater by 18 inches. It should also be closer to the water heater.

I doubt you’ve seen some that are connected to a copper pipe that sticks straight up in the air. Although this might still work, it isn’t recommended. If the copper pipe snaps at any point, your basement will turn into a swimming pool.

You should save your effort and get a universal expansion tank mount. These mounts fit with almost every tank and are likely to keep yours secure.

Acquire Relevant Hardware

Apart from tank brackets and the expansion tank, additional hardware must complete the project you must acquire. These include a few fittings, some Teflon tape for making a worthy connection, and a fitting that links your expansion tank to the size water lines.

You can use PEX push to link fittings. However, if you have copper, you can do either of the following things: purchase some PEX push that can fit fittings because they connect PEX and copper pipes, or acquire a copper fitting and learn how to braze them.

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You might be forced to cut a small part out of the copper pipe cold water supply before you insert a PEX tee-fitting. However, this is a simple task that you can do by yourself.

If you have galvanized steel pipes, it’s time to replace them.

Mount Bracket and Prepare Tank

The first thing you should do here is using Teflon tape to attach the connection fitting to the end of your expansion tank. It would be best if you remembered that the fitting you require on the side connecting to your expansion tank is ¾ female. Your copper pipe or size PEX, on the other hand, is ½ inches.

You can proceed to have the expansion tank bracket mounted. The mounting is necessary before you attach the expansion tank.

TIP: Always confirm that the air valve on the opposite of the water connection is reachable and there is enough room for attaching a bicycle pump. At some point, you’ll need it if you need to adjust the pressure. For instance, if the water pressure is lower or higher than 50 PSI, you must release pressure or pump the tank to match the pressure within the water system. Get the pressure as close as possible to the 50 marks. It’s essential to check and adjust the pressure before mounting the tank.

Turn Off the Water Supply and Mount the Tank

At this point, turn off the water supply to your home. It would be best to open the lowest faucet to drain water pressure from the water lines. Next, you can turn off the water heater and mount your expansion tank on the tank bracket.

Add a Tee-Fitting

Hold or place a towel below the point that you’ll insert a tee-fitting into the hot water tank’s cold water line. You’ll notice residual water there that will leak. You can then cut your supply line where you would like to insert the tee-fitting.

Use the tee-fitting to estimate how much you must cut the line for the tee to fit. Then, depending on how you run your PEX, you can bend it so that you don’t have to cut out any part at all.

Take note of the expansion tank’s direction, and the line between the tee-fitting will run. You must insert the tee-fitting in such a way that the connection linking to your expansion tank faces in that direction. Then, push and crimp the other two joints to the tee-fitting.

Connect the Expansion Tank to the Tee

Cut a piece of Pex that runs between the tee-fitting and the expansion tank. If there are any other fittings between these two, you’ll have to cut several pieces of PEX to link them as well.

Quality Control Test

Once you have connected all the fittings and the complete line between the cold water supply and the tank is running, you can now test for leaks. The faucets that you turned on to drain out water and pressure should remain open at this point.

You can then open the valve linking your home to the main water supply. Close the faucet as soon as you see a steady stream of water flowing out. Confirm that there are no leaks on all the fittings that you installed.

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If you notice leaks, you should turn off the supply to your home, drain water and pressure again using the same faucet, and check the new fitting connections. Leaking ones will require more pushing or crimping to acquire a better joint.

Once you’re sure that the connection is fixed, go through the turn-on process again.

Hot water

Finally, restart the hot water tank.

Need more information on water heater expansion tanks? Check out this YouTube video below.

Why is the Expansion Tank on the Cold Water Side?

As we have seen above, the water heater expansion tank is placed on the cold water side of the water system. This can be attributed to the fact that the tank isn’t insulated.

When the expanded water volumes get into the tank, it’ll cool due to being closer to the cold water. Therefore, the expanded water passes through the cold water before leaving through the faucets.

Should My Expansion Tank Be Hot?

One of the most common questions is whether the water heater expansion tank should be hot. Unfortunately, the outright answer is no. The top section of the tank should be warm, while the bottom part should be at room temperature.

If the whole tank is warm, there is a high chance that the entire tank is full of hot water. The situation is only possible in cases where the diaphragm fails.

Conclusion

It is now clear that the expansion tank installation involves splicing into a cold water pipe above the water heater. A small air-filled tank is attached to act as an expansion chamber that controls any rise in the volume of water. Since this is a safety device installed on water heating systems to protect fixtures and pipes, you must comply with any available plumbing codes where applicable.

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FAQs

Where are Thermal Expansion Tanks Installed: Illustrated Guide - Home Inspection Insider? ›

Expansion tanks are installed on the cold water pipe above the water heater. Generally, expansion tanks are installed in an upright position. However, they can be installed inverted or on their side, provided it is strapped for support.

Where should an expansion tank be located? ›

The expansion tank (potable water type) should be installed on the inlet cold-water line. It can be installed anywhere in the building on the cold-water supply (after the regulator). It is usually installed by plumbers on the cold-water inlet of the water heater.

Where does expansion tank go on heating system? ›

An expansion tank is a small tank divided in two sections by a rubber diaphragm. One side is connected to the pipes of the heating system and contains water. The other side is dry and contains pressurized air, set at approximately 12 psi. As hot water enters the heating system, the pressure in the system increases.

How far does an expansion tank need to be from the water heater? ›

The items which should be installed in sequence in the cold water line are (1) the EXPANSION TANK must be installed at least 18 inches away from the cold water inlet fitting on the water heater, (2) the PRESSURE GAUGE, and (3) the PRESSURE REDUCING VALVE, if required, see Figure 1.

Can a thermal expansion tank be installed on the hot water side? ›

If using a tank for hot water expansion it can be on the cold feed line, but must be after any check valve. If there's no check valve, it can be anywhere on the cold side.

Can expansion tanks be installed horizontally? ›

Expansion tanks can be installed in any direction. Whether oriented uprightly, horizontally, or even upside down, the expansion tank will function properly without any adverse effects.

Do all boilers have expansion tanks? ›

An expansion tank is required on all closed loop heating boiler systems. As a boiler heats the system water, the water will expand in volume.

Where is the expansion vessel on a combi boiler? ›

Expansion vessels, also known as expansion tanks, keep the pressure in a combi boiler stable while water heats and cools. They are typically located inside the boiler casing.

How do I find the expansion vessel on my boiler? ›

How to check an expansion vessel - YouTube

Do all water heaters need an expansion tank? ›

Short answer? If your home has a “closed” plumbing system, then yes, you'll need an expansion tank. You see, homes have either an open or a closed plumbing system.

Why must the expansion tank always be located higher than the boiler? ›

The relief valve would constantly go off. Why must the expansion tank always be located higher than the boiler? The pressure relief valve _____. must relieved at or below the maximum allowable working pressure of the vessel/boiler and must be capable of relieving more energy the system can produce.

Do I really need an expansion tank on my water heater? ›

In a “closed” plumbing system, water can't flow back into the city water lines once it enters your home's plumbing. Now that might not seem so bad but if you don't have an expansion tank, a closed system doesn't give expanded water any route for escape, causing damage to your home's water heater and plumbing.

Why must the expansion tank always be located higher than the boiler? ›

The relief valve would constantly go off. Why must the expansion tank always be located higher than the boiler? The pressure relief valve _____. must relieved at or below the maximum allowable working pressure of the vessel/boiler and must be capable of relieving more energy the system can produce.

What kind of expansion tank must be installed above the highest terminal unit? ›

What kind of expansion tank must be installed above the highest terminal unit? Open-type.

Why install an expansion tank on a water heater? ›

The expansion tank is designed to handle the thermal expansion of water as it heats up in the water heater, preventing excessive water pressure. If water pressure gets to high it can damage valves in plumbing fixtures, joints in supply pipes and the water heater itself.

How big should an expansion tank be? ›

As a general rule, the bigger the water heater, the bigger the expansion tank. For a 50-gallon water heater, you require a 2-gallon expansion tank. Depending on how high your water pressure is, however, you may need to go up a size to a 4.5-gallon expansion tank.

In most cases, most local plumbing codes must install an expansion tank when you install a new water heater on the municipal water supply.. Expansion tanks are installed on the cold water pipe above the water heater.. Where would you install a new expansion tank?. The first step is to turn off the mainline supply of water that connects directly to the cold water side of the heater.. Release pressure from the water heater tank by opening the drain on the hot side of the closer faucet and the water heater.. For this project, you need a good plan to run a branch line off to the expansion tank from the hot water tank cold water application.. However, if you have copper, you can do either of the following things: purchase some PEX push that can fit fittings because they connect PEX and copper pipes, or acquire a copper fitting and learn how to braze them.. You might be forced to cut a small part out of the copper pipe cold water supply before you insert a PEX tee-fitting.. Next, you can turn off the water heater and mount your expansion tank on the tank bracket.. Once you have connected all the fittings and the complete line between the cold water supply and the tank is running, you can now test for leaks.. If you notice leaks, you should turn off the supply to your home, drain water and pressure again using the same faucet, and check the new fitting connections.. As we have seen above, the water heater expansion tank is placed on the cold water side of the water system.

A water heater expansion tank (also known as a thermal expansion tank) is a safety device that can help reduce the risk of damage to your water heater and plumbing system due to pressure built-up in the plumbing system.. When a new water heater is installed on a closed system, an expansion tank is required by building codes.. If you have a private well water system, you may also be wondering if a water heater expansion tank is required?. In this case, your well water system is closed, and an expansion tank will be required on your water heater.. An open water heater system allows hot water from the water heater to pass freely from the water heater tank into the cold water supply line and (if the pressure is really high) eventually back into the municipal water system.. A closed water heater system means that the hot water cannot expand into the cold water supply beyond the shut-off or check valves.. As mentioned above, a water heater expansion tank is a safety mechanism that reduces possible pressure damage to your plumbing system.. Because water naturally expands when it is heated (a process is known as thermal expansion), extra water volume is created every time the tank fires up.. This additional water volume causes an increase in pressure, which, if significant enough, can damage your water heater, plumbing fixtures, and water pipes over time.. In an open plumbing system, expanding water can flow back into the city water supply using a two-way valve, thus eliminating the need for a water expansion tank.. Installing a water expansion tank is best when done immediately following the installation of a new water heater.. In conclusion, a water expansion tank is also called a thermal expansion tank.. However, in a closed system similar to that in most North American homes, the excess water volume has nowhere to go, therefore requiring a water expansion tank to reduce the risk of high-pressure damage to your water heating unit.

The good thing about an expansion tank is that it helps to regulate air and water pressure in the water system.. If, by any chance, the leak is from the pipe found at the top of the expansion tank, try tightening the fitting by yourself.. The function of an expansion tank is to prevent such an air block from ever happening.. Steel tanks usually combine air and water inside to maintain pressure.. There is a high chance that the tank will not hold air pressure after filling it with excess water or completing the fix.. If this is the case, then you must replace the whole diaphragm.

Copper fittings and pipes are used to make connections throughout the installation process.. The expansion tank is connected to the cold water pipe by a 3/4-inch fitting, which is threaded or sweat-soldered to the cold water pipe, or by a short piece of pipe.. The first step is to turn off the mainline water supply that is directly connected to the cold water side of the heater The next step is to connect a hose to the drain valve below the heater and run it to the other end of the nearest drain The final step is to turn off the mainline water supply that is connected to the hot water side of the heater By opening the drain on the hot side of the closerfaucet and the water heater, you may relieve pressure in the tank of the water heating system.. Once you have connected all of the fittings and the whole connection between the cold water supply and the tank is operational, you can begin testing for leaks to ensure that there are none.. Have a question or need more information about water heater expansion tanks?. Pressure gauges for PEX systems are rather affordable, and they will keep you informed about the water pressure in your plumbing system.. A branch line connects your water heater’s expansion tank to your cold water heater’s expansion tank when the cold water being heated by your water heater expands.. It should be installed as near to the water heater as feasible, and at least 18 inches above the water heater itself.. Additional supplies, such as fittings to connect your tank to the appropriate size water pipes in your home, teflon tape to ensure a secure connection, and at least a few fittings will be required in addition to your tank and bracket.. The expansion tank on the water heater serves two purposes: first, it absorbs expansion as the water heats because there is nowhere else for it to go unless a faucet is open, and second, it prevents the T P valve on the water heater from dripping and wearing out before its lifespan because it is the only place for the expansion to go.. Here’s all you need to know about the expansion tank, which is often ignored.. Having an expansion tank built on your home’s water supply line is usually suggested if you have a ‘closed-loop system,’ which can be created by any type of check valve or pressure regulating valve that has been installed on your water supply line.

Installation of an expansion tank may be required by your local building code when you are installing a new water heater, or it may be a retrofit project installed to add protection to an existing water heater.. Water expands as it heats up, and without an expansion tank attached to the water heater, a closed plumbing system can experience damage from this thermal expansion .. An expansion tank provides space for this expanding water, thereby reducing pressure on the water heater tank, and on the pipes and fixture.. Thermal expansion tank Dielectric water heater union Pipe wrench or channel-lock pliers (2) 3/4-inch copper female-threaded unions Pipe-sealing tape 3/4-inch copper tee-fitting 3/4-inch copper pipe Additional 3/4-inch copper fittings (as needed) Plumbing soldering equipment (if needed) Copper flex pipes (if needed). An expansion tank is generally installed directly above the water heater by means of a tee-fitting installed in the cold water delivery pipe.. The expansion tank is usually installed vertically, though it is acceptable to install it horizontally if it is necessary because of space limitations.. The plumbing fittings you will need depends on the type of plumbing pipes you have and on how the expansion tank is oriented, but most commonly the connections are made with copper pipes and fittings.. The expansion tank itself usually has a 1/2-inch or 3/4-inch threaded fitting that is joined into the cold water pipe by means of tee fitting and short lengths or threaded or sweat-soldered pipes.. Install a short length of copper pipe and a tee-fitting to the adapter on the water heater's dielectric union.. Complete the installation by connecting the top outlet on the tee-fitting to the cold water supply pipe, using whatever pipes and fittings are necessary.. If necessary, the expansion tank can be installed a foot or two away from the water heater, provided it is properly spliced into the cold water line.. Most professional plumbers choose to replace the dielectric union with a new one when an expansion tank is added to an existing water heater.

When water is heated in a water heater, the water expands, if possible.. The cold water in the tank is then heated, but when there is no subsequent hot water usage, the heated water has no room for expansion.. The heated water expands back into the cold water supply.. The hot water will expand back into the cold water supply if there are no restrictions, such as check valves, in the supply line.. If there is a check valve in the cold water supply line to the water heater, there is no opportunity for the heated water to expand.. For water service system sizes up to and including 2 inches, a device for controlling pressure shall be installed where, because of thermal expansion, the pressure on the downstream side of a pressure-reducing valve exceeds the pressure-reducing valve setting.. Where a backflow prevention, check valve or other device is installed on a water supply system utilizing storage water heating equipment such that thermal expansion causes an increase in pressure, a device for controlling pressure shall be installed.. A device is also required to control thermal expansion when there is a backflow preventer or check valve installed on the water supply system.. The device to control thermal expansion can be a thermal expansion tank or a relief valve.. A thermal expansion tank is also a device designed to prevent an increase in pressure from thermal expansion.. Although the IPC does not provide specific details about where to terminate the relief valve discharge, I follow the requirements given in the code for water heater relief valves.. In general, I believe the best method to control thermal expansion from heated water in a water heater is to install a properly sized thermal expansion tank in the cold water supply to the water heater.

“Why did my plumber tell me I need a water heater expansion tank?”. However, if a plumber has installed a check valve or a pressure regulating valve also known as a ‘PRV’ on the water supply line coming into your home, pressure from thermal expansion can start to build up inside your home's plumbing system.. With a properly installed thermal expansion tank, that excess pressure will be released before it can stress your home's plumbing.. The expansion tank pictured above is a 2-Gallon thermal expansion tank that Jennings Plumbing Services installed on a brand new 50-gallon water heater in a residential home.. On the bottom, there is a threaded connection where the expansion tank attaches to the water heaters plumbing system.. The 5 Gallon versions used on dual water heater set up or 100-gallon water heaters are just a little smaller than a water cooler.. When the pressure supplied to your home is at the proper level (between 40 and 80 P.S.I.). In this instance, if your thermal expansion tank is working properly there will be no difference in pressure.. One other quick and surefire way of testing your thermal expansion tank's integrity is to perform a quick test on the valve on top of the tank.

Are you worried excessive water pressure from your water heater tank will damage the unit, water supply pipe joints, and plumbing fixture valves?. Sizing a thermal expansion tank requires knowledge of water heater capacity.. An 80-gallon water heater can have a 2-gallon expansion tank if the supply pressure is 40 PSI.. You will also need a dielectric union, female copper pipe adapters, short-length copper pipes, tee fitting, and Teflon tape or pipe joint compound.. The thermal expansion tank sits between the water heater and the cold water supply line.. As such, it would be best to determine the water pipe supplying cold water to the water heater.. Hot water heater expansion tank installation requires mounting the expansion tank above the water heater.. Secure a short copper water pipe to the adapter and add a tee-fitting.. You can sweat-solder the joint between the adapter and the tee-fitting for a more secure connection.. Secure a female pipe adapter on the expansion tank pipe’s other end using a push-fit connector or sweat-soldering.. You are almost complete with the thermal expansion tank installation.. Wrap Teflon tape around the expansion tank’s threaded fitting before fastening it to the horizontal expansion tank pipe’s threaded adapter.. Secure the expansion tank in its mounting bracket.. Use the correct pipes and fitting to connect the tee fitting’s top outlet to the pipe supplying cold water to the water heater.. Did you find our guide on how to install a water heater expansion tank beneficial?

Videos

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4. A Home Inspection Done Right
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5. Home Inspection of a Boiler
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6. Detailed Home Inspection According to a Standard of Practice
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