What is Thermal Expansion in a Plumbing System? (How a Thermal Expansion Tank or Valve Can Be Key To Your Home’s Safety)

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A thermal expansion tank or valve protects your home from leaks caused by thermal expansion. Thermal expansion is a phenomenon that occurs in plumbing systems when water heats up. As water temperature increases, its volume expands, which can lead to a rise in pressure within a closed plumbing system. In homes with modern plumbing systems, water heaters often operate in environments where backflow prevention devices or check valves are installed, creating a closed system. Without a way to accommodate the expanded volume of water, this pressure can build up, potentially leading to damaged pipes, leaks, or even failure of the water heater itself.

To put it simply, when water heats up, it needs more space. If the system doesn’t allow for this, the resulting pressure can strain your plumbing system and appliances. Left unchecked, thermal expansion can cause costly damage, decrease the efficiency of your water heater, and compromise the longevity of your plumbing fixtures. A properly installed thermal expansion tank can mitigate these risks by providing a space to absorb the expanded water volume.

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What is a Thermal Expansion Valve?

A thermal expansion valve (TEV) is a plumbing device that relieves excess pressure caused by thermal expansion. When pressure inside the plumbing system exceeds a predetermined threshold, the valve opens to release small amounts of water, effectively reducing pressure and preventing damage to the system.

While the pipe connected to this valve releases a small amount of water during pressure build-up, a large or continuous amount of water flowing out indicates a significant pressure problem. Customers often call us stating that a pipe coming from their home is leaking water. This is similar to having a running faucet in the home and needs to be addressed quickly. Normally, this is a symptom of a larger pressure problem. Oftentimes, the pressure relief valve does need to be replaced once it has been opened due to running water from high pressure, but this is secondary to resolving the high-pressure issue. Additionally, it is crucial to ensure that the pipe connected to this valve drains in a code-compliant manner to avoid flooding or water damage. Proper drainage setup can prevent water from pooling around your home, which might otherwise lead to costly repairs and hazardous conditions.

Benefits of a Thermal Expansion Valve

1. Pressure Relief: Automatically releases pressure, safeguarding your plumbing system.
2. Protection for Fixtures and Appliances: Prevents excessive pressure that could damage water heaters, faucets, and other fixtures.
3. Cost-Effective Solution: Simple to install and maintain, making it an affordable way to address thermal expansion.

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What is a Thermal Expansion Tank?

A thermal expansion tank is another solution to manage the effects of thermal expansion in plumbing systems. Unlike a thermal expansion valve, which releases excess water, a thermal expansion tank is designed to absorb the increased volume of water. It consists of a small tank with a bladder or diaphragm inside that separates the water from an air cushion. The air compresses as water expands, providing a safe space for the additional volume. Homeowners often turn to thermal expansion tanks for their efficiency and long-term protection against pressure fluctuations.

Benefits of a Thermal Expansion Tank

1. Consistent Water Pressure: Absorbs the expanded water to maintain steady pressure in your system.
2. Prolongs Appliance Lifespan: Reduces wear and tear on water heaters and other plumbing fixtures.
3. Minimizes Water Waste: Unlike valves, which discharge water, tanks store it, making them a more environmentally friendly solution.

Comparing Thermal Expansion Valves and Tanks

While both devices address thermal expansion, their methods differ:

• Thermal Expansion Valves: Release water to relieve pressure. Cost-effective but may result in water waste because when water drips to relieve pressure, it is lost to the plumbing system.
• Thermal Expansion Tanks: Store the expanded water, maintaining pressure without water loss. They require slightly more space and initial investment but provide a reliable and sustainable solution.

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How Do You Know You Have a Problem with Your Pressure?

• Signs of High Pressure: Dripping faucets, banging pipes (water hammer), or frequent activation of the water heater’s relief valve. In other words, you may see water running out of your thermal relief valve. Customers often call us stating that a pipe that comes out of their home is leaking.
• What is Normal Pressure? Most residential plumbing systems operate efficiently at a pressure of 60-80 psi (pounds per square inch).
• What Should You Do If Your Pressure Is High? If you suspect excessive pressure, take immediate action by checking the pressure and consulting a plumbing professional.

How Do You Check Your Pressure?

Properly regulated pressure is essential to a healthy plumbing system. High pressure can lead to pipe bursts, running toilets, dripping faucets, and even shorten the life of your water heater. The water pressure in your home is maintained by your pressure regulating valve. While these can be adjusted to some degree, if you find that you have very high pressure, your valve has likely failed and needs to be replaced.

To measure water pressure, use a water pressure gauge. Attach it to an outdoor faucet or hose bib, turn on the water, and note the reading. It’s important to ensure that this faucet or hose bib is located after your pressure regulating valve. A hose bib in the front of your home, for example, is likely not after the PRV, and the pressure there will always read high. Be cautious when checking the pressure at the boiler drain of your water heater, as sometimes an aging water heater boiler drain can have trouble completely closing again.

Additionally, you cannot check your water pressure accurately if there is any water running in your home or if there are active leaks. Running water alters the pressure reading, leading to inaccurate results. Before testing, ensure all faucets, showers, and appliances such as dishwashers and washing machines are turned off. If you suspect a leak, address it first to prevent skewed pressure readings or further complications in the system.

If the pressure exceeds 80 psi, you may need to hire a plumber to replace your pressure regulating valve.

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Case Study: Resolving Thermal Expansion Issues in Duluth, GA

Recently, a homeowner in Duluth, GA, contacted us while preparing to sell their home. During the buyer’s inspection, the plumbing system did not pass due to a failing thermal expansion tank. The inspection revealed high water pressure that needed immediate attention to meet code compliance.

Our team quickly identified the root cause of the problem: a faulty pressure regulating valve (PRV). The high pressure was not only causing strain on the plumbing system but had also rendered the existing thermal expansion tank ineffective. To resolve the issue, we replaced the pressure regulating valve, effectively bringing the water pressure back to a safe range. We also installed a new thermal expansion tank, ensuring the entire system met code requirements and functioned reliably for the new

homeowners.

Thanks to these repairs, the home’s plumbing system was compliant and ready for sale, providing peace of mind for both the seller and the buyer. This case highlights the importance of addressing high pressure problems promptly and ensuring that all components, such as expansion tanks and PRVs, are functioning correctly.

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Both thermal expansion valves and tanks are valuable tools in protecting your plumbing system from the damaging effects of thermal expansion. If you’re unsure which option is right for your home, consult a licensed plumber to assess your system and recommend the best solution. Thermal expansion tanks, in particular, offer a sustainable and reliable way to safeguard your plumbing from the risks of pressure build-up.