Ever wondered what that small tank attached to your water is? that is called an expansion tank and is actually pretty important. Its purpose is to handle the thermal expansion of water as it heats up in the water heater, preventing excessive water pressure. If pressure gets too high, it can cause ruptures throughout the rest of your system. If you ever have any questions or see that your water heater is missing an expansion tank, then call Royal Flush, the best plumber in Deactur, GA.