What Is A Boiler Expansion Tank?


Have you ever feared your water heater might explode? Or maybe you’ve been scared by a loud boom when you turn off your shower water? Have you ever had an HVAC professional tell you your boiler expansion tank needs to be replaced, but no explanation of why? Fear no more! A boiler expansion tank is a key component of your water heating system and there is much to know about them before deciding if you need one.

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What Is A Boiler Expansion Tank?

A boiler expansion tank is a small tank that sits atop the main water tank of your water boiler to provide room for water to escape when the heated water expands. In the middle of the expansion tank sits a diaphragm that separates the tank into two sections–one for the expanding water to escape to, and the other to act as an air cushion that accommodates the changes and regulates the pressure building from the heating water.

Although expansion tanks used to just be a single-section unit, the design was improved with two sections of the tank to prevent air from entering the boiler and causing corrosion. Expansion tanks are used to assist in the processes of heating water or chilling it. They are particularly helpful in eliminating some causes of water hammer, or hydraulic shock. Read on to find out more about water hammer and its symptoms.

What Is  A Water Hammer?

Water hammer, or hydraulic shock, is a common phenomenon that can lead to the wear and tear of your water heating unit. Have you ever noticed a loud bang when you turn off your water in a faucet or bathtub? That noise is due to the water flow abruptly changing direction and sending out shock waves. It can cause the piping and heating systems to deteriorate as well as be very annoying! You can install a boiler expansion tank to help prevent water hammer and preserve your heating system.

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Kinds Of Boiler Expansion Tanks

There are two different models of boiler expansion tanks: the steel type and the bladder type. Let’s take a closer look at each.

Steel Type Expansion Tanks

image of a boiler expansion tank

Steel type expansion tanks have been in use for decades and can often be seen in older homes. In this model, there is no diaphragm, so the water and air do touch each other. Hence the use of a steel tank to avoid corrosion as much as possible. These heating system tanks should have a small window, called a sight glass, that assists in viewing the ratio of water to air in these tanks.

The correct ratio of water to air depends on many factors. These include what your convectors are made out of (usually iron or copper), how much water your heating tank can hold, and other factors. Steel tanks can have problems due to the mixing of air and water, such as corrosion, flooding the tank, or faulty gaskets. A professional HVAC contractor can help to fit your water heater/boiler with the correct size of steel type expansion tanks.

Bladder Type Expansion Tanks

The bladder tanks’ crucial difference from the steel tanks is that they contain a diaphragm that separates the water and air within the expansion tank. This leads to longer-lasting capabilities but does not eliminate the issue of air in the system entirely. In a heating system involving a bladder expansion tank, the air still separates from the water and must be removed from the system. You should use the help of a professional to ensure the correct amount of pressure within the system. An HVAC professional can also help to determine what size bladder expansion tank you need for your own boiler tank.

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Is Your Expansion Tank Working Properly?

image of a boiler repair

Do you have an expansion tank but aren’t sure it’s working properly? One very common reason they can malfunction is that the pressures within the chambers aren’t correct. Steel expansion tanks have a pressure relief valve that may be venting hot water, indicating that your pressures within the tank have a problem. Checking the water level through your sight glass will allow you to see if pressure is indeed off. For bladder tanks, check the pressure on the airside of the diaphragm to see if the lines need to be drained of water so that the bladder can refill with air.

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Many heating systems contain one or several boiler expansion tanks. However, very few people understand what they are for. These nifty reservoirs and their systems help to regulate the pressure within a heating system when heating water in the boiler tank. Thus, they help avoid many boiler tank issues such as water hammer and overpressurization. They can help to preserve your heating system for many years to come. Call McAllister Energy today to get your free installation quote!

Call McAllister Energy For All Of Your HVAC Requirements

McAllister EnergyMcAllister Energy offers superior heating and cooling services in Camden County, New Jersey. We hire professionally certified technicians who can provide you with excellent HVAC tune-ups, repairs, installations, and replacements. Each of our techs has the knowledge and experience to service your HVAC system correctly.

McAllister Energy guarantees the most competitive heating and cooling service costs in the area. Our maintenance services can improve your comfort, increase your energy efficiency while reducing your home energy costs. If you happen to need an HVAC repair or replacement system, we can recommend the best one for your home while staying within your budget. We back all of our work with a guarantee to ensure your satisfaction. To schedule a service appointment, give McAllister Energy a call today. We offer free, in-home estimates.

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