You are currently viewing Do Tankless Water Heaters Need Expansion Tanks

Do Tankless Water Heaters Need Expansion Tanks

The question of whether or not tankless water heaters need expansion tanks is one that has been asked numerous times. It’s not a surprising query considering how vital both of these units are to your home’s comfort and convenience. So, let’s dive in and explore this topic deeply.

What is a Tankless Water Heater?

A tankless water heater, as the name implies, does not use a tank to store hot water. Instead, it heats water on demand, meaning it only heats water when you need it. This type of water heater provides hot water instantly and can significantly reduce energy costs since it eliminates the need to constantly heat a reservoir of water.

When you turn on a hot water tap, cold water travels through a pipe into the unit, where it’s heated either by an electric element or a gas burner. The hot water then flows directly to your faucets, showers, or appliances. A tankless water heater can deliver a constant supply of hot water, providing you don’t exceed its flow rate capacity.

Understanding Expansion Tanks

An expansion tank, on the other hand, serves a different primary purpose. This device is designed to handle the extra volume of water created when the water in the heater expands as it gets heated. You see, water volume increases as its temperature rises – this is called thermal expansion. And since water is almost incompressible, this additional volume needs somewhere to go.

That’s where the expansion tank comes in. It absorbs this excess volume of hot water thereby protecting your plumbing system from damage caused by increased pressure. The expansion tank has two sections separated by a diaphragm: one side contains air under pressure and the other side connects to the house’s plumbing system.

The Relationship Between Tankless Water Heaters and Expansion Tanks

Now that we’ve covered what both a tankless water heater and an expansion tank do, let’s examine their relationship. The truth is, a tankless water heater doesn’t typically require an expansion tank. Why? Because the water in a tankless system is not stored and heated continuously, meaning thermal expansion isn’t as much of an issue as it is with traditional water heaters.

However, this doesn’t mean you should completely disregard expansion tanks if you have a tankless water heater. Local building codes or particular circumstances might necessitate the use of an expansion tank even with a tankless system.

When You Might Need an Expansion Tank with a Tankless Heater

Even though it’s not usually necessary, there are instances when installing an expansion tank with a tankless water heater can be beneficial. For example, if your plumbing system uses a check valve or pressure reducing valve (PRV), which prevents water from flowing backwards through the pipes, thermal expansion could cause pressure to build up in the system.

In such cases, having an expansion tank can help to absorb the increased volume of heated water and alleviate the potential pressure buildup. So while not strictly required, an expansion tank can serve as a useful safety measure in certain situations.

See also  How To Tell The Difference Between Cellulose And Asbestos Insulation

The Role of Building Codes

Local building codes can also play a part in determining whether or not you need an expansion tank for your tankless water heater. Some municipalities require an expansion tank for any type of water heater, including tankless models. This is usually due to specific local conditions or concerns regarding infrastructure.

If you’re uncertain about whether this rule applies to you, it may be worth contacting your local building department or consulting with a licensed plumber who is familiar with your area’s codes and regulations.

How to Install an Expansion Tank

If you find that you do need an expansion tank for your tankless water heater, it’s generally best to have it installed by a professional plumber. This isn’t a DIY task unless you’re extremely knowledgeable in plumbing systems.

The installation involves connecting the expansion tank directly to the water line near the water heater, and properly setting the air pressure in the tank to match the water pressure in your plumbing system. It’s also crucial to ensure that the tank is securely mounted, either vertically or horizontally, according to the manufacturer’s instructions. Again, this isn’t a task to undertake lightly and is best left to a professional.

If you’re having a new tankless water heater installed, you can also discuss with your plumber whether adding an expansion tank at the same time would be beneficial or necessary.

In summary, while tankless water heaters don’t inherently require expansion tanks due to their on-demand heating mechanism, there might be circumstances or local codes that make an expansion tank a prudent addition. As always, when in doubt, consult with a qualified plumbing professional for advice tailored to your specific situation.

The Importance of Sizing an Expansion Tank

Regardless of whether the expansion tank is being installed with a tankless water heater or a traditional one, proper sizing is crucial. The size of the expansion tank must be sufficient to accommodate the extra volume of water produced during the heating process.

Notably, the size of an expansion tank is not measured by its physical dimensions but by its water holding capacity, which is usually expressed in gallons. The sizing of an expansion tank is typically based on the water heater’s capacity and the incoming water pressure.

Considerations for Expansion Tank Maintenance

An expansion tank, just like any other component of your plumbing system, requires regular maintenance to ensure optimal operation. It’s important to periodically check the pressure inside the tank to ensure it’s properly balanced with the water pressure in your system.

Moreover, you should keep an eye out for signs that the expansion tank may be failing. This could include visible leaks or a noticeable decrease in water pressure. If you suspect a problem, it’s wise to call a professional plumber for an inspection as soon as possible.

The Impact of Water Hardness on Tankless Heaters and Expansion Tanks

Another factor to take into consideration when dealing with tankless water heaters and expansion tanks is the hardness of your water. Hard water, which is high in minerals like calcium and magnesium, can lead to scale buildup inside your plumbing fixtures.

This scaling can negatively affect both the efficiency and lifespan of your tankless water heater. In extreme cases, it can also cause damage to your expansion tank. Therefore, if you live in an area with hard water, you might need to install a water softener system to protect your plumbing components.

The Role of Safety Valves

Another component that plays a role in managing pressure in your plumbing system is the safety valve. This device, also known as a pressure relief valve, is designed to open and release water if the pressure inside the system becomes too high.

A safety valve serves as an additional layer of protection for your plumbing system, helping to prevent damage due to excessive pressure. It’s important to note, however, that while a safety valve can help manage pressure, it doesn’t replace the need for an expansion tank in systems where thermal expansion is a concern.

Understanding Thermal Expansion in Different Climates

The impact of thermal expansion can vary depending on the climate where you live. In colder climates, the incoming water is often significantly colder than in warmer regions. Therefore, the process of heating the water results in a greater increase in volume, which could potentially lead to more pressure build-up in your plumbing system.

See also  How Big Is A Tiny Home

Conversely, in warmer climates where the incoming water is already relatively warm, the increase in volume from heating may be less substantial. Thus, the potential for pressure build-up due to thermal expansion might be lower.

The Bottom Line

In essence, whether or not you need an expansion tank with a tankless water heater depends on various factors such as local building codes, the specific characteristics of your plumbing system, and even your local climate.

Even though an expansion tank may not be required by default with a tankless system due to its on-demand heating mechanism, certain conditions might warrant its use for protecting against potential damages caused by thermal expansion. As always, when making such decisions about your home’s infrastructure, it’s prudent to consult with a professional who can provide expert advice tailored to your unique circumstances.

Frequently Asked Questions

Do all homes with a tankless water heater need an expansion tank?

Not necessarily. Tankless water heaters heat water on demand and do not store water, so thermal expansion is not typically an issue. However, local building codes or particular circumstances might necessitate the use of an expansion tank even with a tankless system.

How does a tankless water heater work?

A tankless water heater heats water on demand. When you turn on a hot water tap, cold water travels through a pipe into the unit, where it’s heated either by an electric element or a gas burner. The hot water then flows directly to your faucets, showers, or appliances.

Why might I need an expansion tank even with a tankless system?

If your plumbing system uses a check valve or pressure reducing valve (PRV), which prevents water from flowing backwards through the pipes, thermal expansion could cause pressure to build up in the system. In such cases, having an expansion tank can help to absorb the increased volume of heated water and alleviate the potential pressure buildup.

What role do local building codes play?

Local building codes can also play a part in determining whether or not you need an expansion tank for your tankless water heater. Some municipalities require an expansion tank for any type of water heater, including tankless models.

Can I install an expansion tank myself?

Installation of an expansion tank involves some technical aspects and is generally not a DIY task unless you’re extremely knowledgeable in plumbing systems. It’s generally advised to have it installed by a professional plumber.

How does sizing affect the function of an expansion tank?

The size of the expansion tank must be sufficient to accommodate the extra volume of water produced during the heating process. It’s usually calculated based on the water heater’s capacity and the incoming water pressure.

How often should I check the pressure inside the expansion tank?

It’s important to periodically check the pressure inside the expansion tank to ensure it’s properly balanced with the water pressure in your system. The frequency can depend on individual system requirements.

What happens if an expansion tank fails?

If an expansion tank fails, it may lead to visible leaks or a noticeable decrease in water pressure. If you suspect a problem, it’s wise to call a professional plumber for an inspection as soon as possible.

How does hard water affect tankless heaters and expansion tanks?

Hard water, which is high in minerals like calcium and magnesium, can lead to scale buildup inside your plumbing fixtures. This scaling can negatively affect both the efficiency and lifespan of your tankless water heater and can also cause damage to your expansion tank.

What is a safety valve?

A safety valve, also known as a pressure relief valve, is designed to open and release water if the pressure inside the system becomes too high. It serves as an additional layer of protection for your plumbing system.

Does thermal expansion have different impacts depending on the climate?

Yes. In colder climates, the incoming water is often significantly colder than in warmer regions. Therefore, the process of heating the water results in a greater increase in volume, which could potentially lead to more pressure build-up in your plumbing system. In warmer climates, the potential for pressure build-up might be lower.

In Summation

When dealing with tankless water heaters and expansion tanks, the importance of understanding their interplay can’t be overemphasized. While a tankless system’s on-demand heating mechanism may not always necessitate an expansion tank, factors like local building codes, plumbing system characteristics, and regional climates may call for one. As such, it’s recommended to always seek professional advice to ensure the optimal operation and longevity of your home water heating system. Hence, knowledge is indeed power – the power to make informed decisions that safeguard your home’s comfort and convenience.