Are Expansion Tanks Required On Tankless Water Heaters

Yes, expansion tanks are required on tankless water heaters. Expansion tanks are used to absorb the additional pressure created when hot water expands as it is heated and enters the plumbing system. The expansion tank helps ensure that the pressure does not exceed a safe level for your pipes and fixtures.

Without an expansion tank, any excess pressure can cause damage to your plumbing system and even result in flooding or other issues such as leaks.

Additionally, having an expansion tank can help extend the life of your water heater by reducing wear-and-tear from high levels of pressure over time. Therefore, while installing a new tankless water heater it is important to also install an expansion tank alongside it.

Expansion tanks are not typically required for tankless water heaters; however, there are certain cases when they may be necessary.

In areas with extremely hard water, or a system that is prone to large fluctuations in pressure, it is recommended that an expansion tank be installed.

Expansion tanks help protect the system from over-pressurizing by providing a space for extra water to expand as it heats up and relieves pressure on valves and other components of the system.

Where to Install Expansion Tank on Tankless Water Heater

One of the most important aspects to consider when installing a tankless water heater is where to install the expansion tank.

The expansion tank should be installed on the cold water line, downstream from the shut-off valve and before the hot water outlet. This will ensure that any excess pressure created by thermal expansion can be safely directed away from your unit, reducing potential damage and ensuring optimal operation.

Are Expansion Tanks Required by Code in Maryland

In the State of Maryland, expansion tanks are not currently required by code for residential hot water systems. However, they are generally recommended to ensure proper functioning of closed loop heating and cooling systems.

Expansion tanks provide a controlled environment in which thermal expansion can occur as heated water expands when pressure builds up inside the pipes.

This helps prevent pressure buildup that can cause damage to plumbing fixtures and appliances connected to your home’s hot water system.

Do I Need an Expansion Tank If I Have a Pressure Tank

If you have a pressure tank in your home, an expansion tank is not necessary. Pressure tanks are designed to absorb the increased volume of water that results when hot water is heated and expands.

The expansion of the hot water is contained within the pressure tank, and does not require an additional expansion tank for storage.

However, if you do choose to install an expansion tank on your plumbing system it can help protect against thermal shock which occurs when large volumes of cold or hot water enter into the plumbing system quickly.

Expansion Tank for Water Heater Required by Code Florida

In Florida, an expansion tank for a water heater is required by code. An expansion tank helps to prevent pressure build-up in the system that could damage pipes or the water heater itself. It also helps maintain high efficiency of the unit and extend its lifespan.

Installing an expansion tank on your hot water heater can help protect it from pressure issues caused by thermal expansion and ensure proper operation for many years to come.

What Size Expansion Tank for Tankless Water Heater

When choosing an expansion tank for a tankless water heater, make sure to determine the correct size for your system.

Expansion tanks come in different sizes depending on the type and volume of hot water used in the home.

Generally speaking, a 3-4 gallon expansion tank should be sufficient for most systems; however, if you have high flow rates or larger volumes of hot water then you may need a larger capacity expansion tank.

Additionally, it is important to check with your local code requirements as some jurisdictions require specific sizing based upon individual circumstances.

Where is the Expansion Tank on a Tankless Water Heater?

The expansion tank on a tankless water heater is typically located close to the main supply line, or between the incoming cold and hot water lines. It is usually housed in an insulated metal box that can be easily accessed for maintenance or replacement purposes.

The purpose of an expansion tank is to protect against over-pressurization due to thermal expansion, which occurs when heated water expands and places excessive pressure on pipes and fixtures.

Expansion tanks absorb this excess pressure by providing a place for it to go, which helps prevent pipe ruptures and other damage due to high pressure conditions.

Depending on your particular setup, you may need professional help installing an expansion tank with your tankless water heater as they require special connections that are not always compatible with standard plumbing systems.

Is an Expansion Tank Required by Code?

The answer to this question depends largely on the regulations in your local area as well as the type of plumbing system you have. In many cases, an expansion tank is not required by code for residential applications; however, some jurisdictions may require them in certain situations, such as when installing a pressurized hot water heater or other high-pressure appliance.

Expansion tanks are also often used in commercial systems to reduce the strain placed on pumps and other equipment due to excessive pressure fluctuations caused by thermal expansion of heated fluids.

By providing a cushion of air that absorbs and releases pressure changes from expanding fluid volumes, expansion tanks can help prevent damage to pipes and fixtures while helping extend the life of these components.

Ultimately, it’s best practice to check with your local building codes regarding requirements for an expansion tank before making any decisions about installation.

What Happens If You Don’T Have Expansion Tank?

If you don’t have an expansion tank installed in your home, you could be facing some serious problems.

Without this important component of a plumbing system, the pressure from hot water heating up in your pipes can cause them to burst or crack over time.

The expanding hot water puts more pressure on the pipes than cold water does and without an expansion tank there is no place for it to go.

In extreme cases, bursts and cracks can lead to flooding as well as costly repairs. An expansion tank also helps improve energy efficiency by allowing heated water to cool before going through fixtures such as showers and faucets – meaning less energy will be wasted while still providing enough heat for comfort.

Installing one is relatively easy depending on the type of system that’s already in place and its size – so if yours doesn’t currently have one then make sure you get it sorted out soon!

What Size Expansion Tank for Tankless Water Heater?

When deciding what size expansion tank is needed for a tankless water heater, it’s important to consider the capacity of the unit.

The size of an expansion tank is usually determined by the amount of water in gallons that can be stored within it. Generally speaking, most residential-sized units will require an expansion tank that holds between two and five gallons.

However, depending on the specific requirements for your particular model of water heater, you may need a larger or smaller sized expansion tank.

Additionally, if your home has multiple bathrooms or showers associated with it then this will also influence the necessary size as well as pressure levels and climate conditions in your area.

It’s best to consult with a professional plumber who can advise you on what type and size of expansion tank would best suit your individual needs before making any purchases.


In conclusion, expansion tanks are not absolutely necessary for tankless water heaters. However, they can be beneficial in certain situations to help regulate the temperature of the hot water and prevent potential damage from thermal expansion.

While installation costs may be higher than with conventional tank-style heaters, it is a worthwhile investment that will save homeowners money in the long run by protecting their plumbing systems from costly repairs due to thermal expansion.

Expansion tanks should always be installed by professionals who understand how to properly size them for each individual application.

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