What Is A Boiler Expansion Tank?

image of a boiler with expansion tank

Have you ever heard a booming sound when you switch off your shower? Did you feel scared that your water heater might suddenly explode? Has an HVAC professional ever told you that you need to have your boiler expansion tank replaced without any further explanations? Don’t fret. This article will help you understand all you need to know about boiler expansion tanks. This way, you can decide if you need one for your home.

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What Is A Boiler Expansion Tank?

A boiler expansion tank is located at the top of the main water tank of the water boiler. When water is heated, it expands. Therefore, the tank is there to provide space so that water can escape when it is heated. The expansion tank has a diaphragm inside that separates it into two. One section is where the heated water escapes to. The other is like an air cushion so that the pressure changes from the heating water is regulated.

It was initially a single-section tank. However, the improved design was made so that air does not enter the boiler and cause corrosion. These small tanks offer significant assistance when you heat or chill water. They help prevent some issues, such as hydraulic shock or water hammer.

Water Hammer Definition

Also called hydraulic shock, the water hammer is a common occurrence that can cause your water heater to wear out faster. If you hear a loud bang whenever you turn on your bathtub or faucet, it is because the water flow suddenly changes direction. It causes shock waves, and this is the sound you hear. As a result, the pipes and the heating systems in your home deteriorate. A simple solution to this issue is to install a boiler expansion tank.

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Kinds Of Boiler Expansion Tanks

The two different kinds of boiler expansion tanks are the steel type and the bladder type. Read on and find out more about these two models.

Steel Type Expansion Tanks

image of a boiler expansion tank

This type of expansion tank is often found in older homes. It has no diaphragm, so air and water do not come in contact with one another. This way, corrosion is prevented as much as possible. A steel type expansion tank is also equipped with a small window known as a sight glass. This allows you to see the water to air ratio in the tank.

The right water to air ratio is dependent on various factors. These include the material the convectors are made of, which is typically copper or iron, and your heating tank’s water capacity, among others. Some of the usual problems a steel tank has is a result of water and air mixing. These issues include faulty gaskets, corrosion, and flooding of the tank. Contact your local, trusted technician to help you find the boiler or water heater with a correctly-sized steel type expansion tank.

Bladder Type Expansion Tanks

Unlike the steel tank, a bladder tank has a diaphragm that separates the air and water inside the expansion tank. They tend to last longer as a result, but this does not completely remove the air inside the tank. A heating system with a bladder expansion tank, the air is separated from water and must then be removed from the system. An HVAC expert can help you ensure that your system has the right amount of pressure. They can also help find the correct bladder expansion tank size you need for your boiler tank.

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Is Your Expansion Tank Working Properly?

image of a boiler repair

One of the most common reasons expansion tanks do not work properly is the incorrect pressures within the chambers. Steel expansion tanks are usually equipped with a pressure relief valve that might be discharging hot water. This is an indication that the tank might be having pressure problems. View the water level via the sight glass so you can check if the pressure is off. If you have a bladder tank, check the diaphragm’s airside section to determine the pressure and see if the water needs to be drained so that air can be refilled in the bladder tank.



Your heating system might have one or more boiler expansion tanks. These reservoirs allow your heating system to regulate the pressure during the water heating process. Therefore, problems like water hammer and overpressurization are avoided. Expansion tanks also help prolong your system’s lifespan. Contact Lawes Company today for a free installation quote.

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Lawes Company offers superior HVAC services in Monmouth and Ocean Counties, New Jersey. We only hire professionally certified and trained technicians. Rest assured, our friendly techs can conduct high-quality services, such as maintenance, repairs, installations, and replacements. All our friendly, knowledgeable, and experienced techs can service your HVAC unit accurately.

Our company has the most competitive heating and cooling service prices in the area. We can help improve your comfort, energy efficiency, and indoor air quality with our maintenance services. If you need to replace your current HVAC equipment, we can also find the best make and model to fit your needs and budget. Your satisfaction is important to us, so all our work comes with a guarantee. Book a service appointment with us today. Lawes Company offers free, in-home estimates.

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