It's a common question from so many of our clients."Do I really need an expansion tank on my hot water heater?"

Thermal expansion protection is required on new water heater tanks.

Thermal expansion protection can be done 3 different ways:

  1. installing a thermal expansion tank properly sized for the tank
  2. using a thermal expansion relief valve
  3. using a governor 80 ballcock

Thermal expansion is caused by changing the temperature of the water. When water is heated, water expands. So, 40 gallons of water at 50 degrees coming into the house, when it's heated to 120 degrees is approximately 40.5 gallons of water, an increase of approximately 0.5 gallons. The excess water has to go somewhere, so it either causes leaks in the house, stretches the water pipes in supply lines, leaks out of the relief valve or pushes backwards through the meter (if there is no dual check valve or backflow preventer), but basically when the water has no where to go the pressure in the system increases.

The stress of this increased pressure shortens the life of the water heater and frequently results in pipes bursting, leaking fixtures and running toilets.

A thermal expansion tank is a simple way to solve this problem on most smaller water heater systems. The tank is full of air. When the heater goes through a heat cycle the excess volume of water pushes into the tank and compresses the air, but keeps the water pressure the same. Air is compressible but water is incompressible.

The two other options for thermal expansion protection, (the thermal expansion valve and the governor 80 ballcock) actually dump the extra water down the drain every heating cycle.

These two alternative options are legal and protect against thermal expansion and are generally used in situations where there is no room for a thermal expansion tank or the size of the water storage tank is larger than a standard thermal expansion tank (for example, in an apartment complex there may be 10 water heaters protected by one thermal expansion valve, this situation is only by an engineered design, and is only in a situation where the is no check valves on the individual units).

Why Do We Recommend An Expansion Tank?

First and foremost - our goal is to help you keep your hot water heater running smoothly and safely as long as possible.An expansion tank will help you achieve that goal.

You see, the normal thermal expansion that occurs as the hot water heater actually heats your water can place alot of stress on your plumbing pipes.This stress can cause cracks which then cause leaks and well, we don't have to tell you what happens when your pipes begin to leak.The cost to detect and repair water pipe leaks can be expensive.

As the water in your hot water heater gets hotter and hotter - it expands.Let's say a 40 gallon tank has a water temperature that is curently at 90 degrees Faherenheit.When that water is heated to 140 degrees Fahrenheit - it will expand by almost one-half gallon.

You can help to prevent this extra expense by having an expansion tank installed.

What Is An Expansion Tank?

Expansion tanks (aka Thermal Expansion Tanks) are essentially safety devices to help you minimize the risk of damage to your hot water tank.They are an "add on" to your existing hot water heater and are often installed on the water supply pipe to the water heater.Normally this is on the wall next to or very close by your hot water tank.

They take up very little space but can save you alot of money down the road, especially as your tank ages.

Expansion tanks come in 2 gallon and 4.5 gallon sizes.We can help you to choose the proper one for your home.


If you are considering adding an expansion tank to your hot water heater. call us today at 770-505-8570. We will be happy to answer any of your questions about the project and cost.We are available 24 hours a day, 7 days a week.

We Offer Water Heater Services in Metro Atlanta and Surrounding Areas

Fulton County, Bartow County, Cobb County, Paulding County, Cherokee County, Gwinnett County, and Douglas County.

Acworth GA, Atlanta GA, Austell GA, Cartersville GA, Doraville GA, Douglasville GA, Hiram GA, Kennesaw GA, Lawrenceville GA, Lithia Springs GA, Loganville GA, Mableton GA, Marietta GA, Powder Springs GA, Rockmart GA, Roswell GA, Smyrna GA, Tucker GA, Villa Rica GA, Vinings GA, Woodstock GA, and Surrounding Communities.