Close this search box.

What is a Water Heater Expansion Tank?

As water is heated, it expands and creates additional pressure within your domestic plumbing system. This pressure must be adequately controlled. Expansion tanks were developed to relieve the pressure that can build up inside a hot water system.

Why You Need an Extra Tank

In the past, when a hot water heater experienced too much pressure, water from the appliance would flow back through the supply line. This is no longer possible because many municipal water systems are installing backflow preventers on their water meters. The backflow preventer keeps unwanted contaminates that may be found within a domestic plumbing system from entering the water supply.

As the pressure rises beyond acceptable limits in the water tank, it must be relieved in some way to avoid a catastrophic failure of the unit. In most cases, the temperature and pressure relief valve will activate and discharge water from the appliance. This wastes water and energy. In other situations, the tank can rupture or split resulting in a leak. To prevent this, you should install an expansion collection tank.

How the System Works

The collection tank is attached to the water supply line prior to its connection to the appliance. The expansion reservoir is like an air filled bladder. As pressure rises inside the water tank, the overflow enters the expansion container rather than being discharged. The water compresses the air in the tank. As you use hot water, pressure is reduced within your home’s plumbing system. The air in the expansion reservoir expands as the water pressure is reduced. The expanding air forces the water back out of the collection container and into the water heater. The expansion reservoir collects water that would otherwise be discharged through the relief valve for later use. The extra space provided by this collection tank reduces pressure within the system and also the stress on the outer shell of the main water tank preventing leaks. This assistance will prolong the service life of the appliance.


If you notice the relief valve activating or signs of a water leak, contact our team of experts at AC by Luquire. We will gladly schedule a convenient time to come by your Eclectic, AL home and test the pressure within your plumbing system. Based on the results, one of our highly trained service technicians can install an expansion tank that will give you the peace of mind that comes from knowing that your system has the safety features that it needs.

Compliance Settings
Increase Font Size
Simplified Font
Underline Links
Highlight Links