Quote:
Originally Posted by Berwin
Why do water heaters in Florida homes have expansion tanks?
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Not just Florida, they are required almost everywhere. The expansion tank helps to maintain a safe water pressure in your house. It has air in the top of the tank that prevents unsafe pressure when the hot water expands due to thermal expansion. It allows the expanding water to push up on the diaphragm that separates the water from the air in the expansion tank.
For example, if you use a lot of hot water by taking several showers, the hot water in the water heater will be replaced with cold water. Then, if you turn off all plumbing outlets and leave the house, the water heater will heat up the cold water in the tank. This will cause thermal expansion and a significant rise in water pressure. The expansion tank allows the pressure to be relieved.