Water Heater Expansion Tank

Why is an expansion tank required?

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When water is heated it expands.  With nowhere to go, this expansion can create enough pressure to cause damage in your home.  To prevent this from happening, code requires an expansion tank.  Combined with the Temperature and Pressure Relief valve this helps keeps your water heater and home safe.  

An expansion tank is a device that helps prevent damage to your water heater and plumbing system caused by excess pressure and thermal expansion. Thermal expansion occurs when water is heated and increases in volume. If the water has nowhere to go, it can create too much pressure in the pipes and the water heater, leading to leaks, ruptures, or corrosion. An expansion tank provides a space for the expanded water to flow into, reducing the pressure and protecting your system.

You may need an expansion tank for your water heater if you have a closed plumbing system, which means there is a device that prevents the water from flowing back to the city lines. This can be a check valve, a pressure-reducing valve, or a backflow preventer. A closed plumbing system creates a single path for the water to flow, and when the water is heated, it can cause a pressure build-up that can damage your system. An expansion tank can help relieve this pressure and extend the life of your water heater and plumbing.  Most homes need an expansion tank today.  

If you are not sure whether you have a closed plumbing system or not, you can check your water meter or main shutoff valve for any signs of a device that blocks the reverse flow of water. You can also perform a simple test by turning off the main water supply, opening a hot water faucet, and observing the water pressure. If the water pressure drops quickly, you have an open system and you do not need an expansion tank. If the water pressure stays high or increases, you have a closed system and you need an expansion tank.

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If you need an expansion tank, you should also consider the size and type of the tank that suits your water heater. There are two main types of expansion tanks: compression tanks and bladder tanks. Compression tanks are plain steel tanks that provide space for the expanded water. Bladder tanks have a membrane that separates the water from the air, preventing the air from being absorbed into the system and causing water-logging issues. Bladder tanks are more common and preferred for water heaters.  The tank must be labeled “NSF” and “for potable use” if you want to use it for domestic hot water systems.  

The size of the expansion tank depends on the size and capacity of your water heater, the water pressure in your system, and the temperature setting of your water heater. You can use a formula or a chart to calculate the size of the expansion tank you need, or you can consult a professional plumber for guidance. Choosing the right size of the expansion tank is important, as a too small or too large tank can cause problems such as water hammer, pressure fluctuations, or reduced efficiency.

The installation of an expansion tank can vary depending on the location and configuration of your water heater and plumbing system. Generally, the expansion tank should be installed on the cold-water supply line, as close to the water heater as possible. You may need to use fittings, brackets, or supports to secure the expansion tank properly. You should also check the air pressure in the expansion tank and adjust it to match the water pressure in your system. You can use a tire pressure gauge and a bicycle pump to measure and change the air pressure in the expansion tank before installing the tank. 

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The installation of an expansion tank requires plumbing skills and tools.  There are many local codes and regulations that must be followed.  Choose a registered plumber for this kind of work.  The cost of installing an expansion tank can vary depending on the type and size of the tank, the complexity of the installation, and the time required to install.  

An expansion tank is a safety add-on to your water heater that can prevent damage, improve performance, and save money in the long run. By understanding how an expansion tank works, how to determine if you need one, and how to choose and install one, you can enhance the safety and efficiency of your water heating system. If you have any questions or concerns about expansion tanks, you can always contact John Wilcox Plumbing Heating and Cooling for advice and assistance.

When making plumbing decisions use a licensed, and skilled plumber to help you with your decision, install it properly, and keep it maintained as needed.  At John Wilcox Plumbing and Heating we use licensed plumbers, Journeyman, and Master Plumbers.  Contact us to install or replace your expansion tank.  

Our Combination Boilers with Hot Water Heater Services

You can always count on our skilled and experienced technicians to give you the best service, from supply to replacement. Our team is always ready to help. Here are a few services that we provide:


Through years of experience and connections, we have a wide variety of combination boilers with water heaters that you can choose from so that you won’t have to look elsewhere.


We will ensure that your water heater is connected correctly and running at its best during the installation procedure.


Our crew can quickly identify the source of the problem and fix your water heater if it is acting up. However, routine maintenance is essential to keep your Combination Boilers with Hot Water heater in good working order for as long as possible and avoid expensive water heater repairs.


The average commercial water heater will survive for six to twelve years with regular servicing. Your water heater should probably be replaced when it shows signs of being close to the 10-year mark. We can provide safety inspections. We will look for worn components, advise you on how old the water heater is, and recommend safety enhancements.

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Here at John Wilcox Plumbing, you can count on us for easy water heater replacement. Rebates and Credits are available for many energy saving water heaters. We have a matrix of rebates and credits available under our Menu / Resources Tab. The US government offers Discounts for high-efficiency installations, such as Natural Gas Utility Credits and Electric Utility Credits. These can be worth hundreds or thousands of dollars if you choose energy saving appliances. We can help you save energy and money. Call us to schedule us to evaluate what you need in your home.

Brands of Combination Boilers with Hot Water Heater We Maintain and Service

Among the most remarkable modern comforts is the ability to have access to hot water, so it’s crucial to get a water tank from a reputable residential water heater provider. Our store carries the following brands:

Brands we service, repair and replace
  • AO Smith ProLine
  • Rheem Manufacturing
  • Bradford White
  • Noritz
  • Whirlpool
  • Rinnai
  • Stiebel Eltron
  • State Select
  • Ruud
  • Navian
  • Takagi
  • Ecosmart
  • Ariston Thermo
  • GE
  • Bosch
  • Rheem
  • Takagi
  • Kenmore / Sears
  • American Standard
  • Noritz
  • Whirlpool
  • Sears

Areas We Serve around Bridgeville, PA

Our unwavering commitment to the commercial and residential water heater industry has allowed us to grow and expand our service regions to include:

Where we serve

Service Areas

Reach Out to Us for Your Water Heater Problems

If you require water heater services, including heat pump high-efficiency water heater services, in your home or commercial property, contact John Wilcox Plumbing today to schedule an appointment. We look forward to working with you!