Imagine the inside of your home’s water heater with too much pressure inside.
In the past, pressurized water that built up would simply drain back into the city’s supply system. But this isn’t always possible. If something is there to prevent this release, you’re going to need another safeguard – which brings us to the water heater expansion tank.
A water heater expansion tank is an additional small thank that is attached to your water heater unit. It is designed to handle that excess water that builds up. So, when the water pressure gets too high, it will flow into your expansion tank instead of damaging your home’s plumbing valves, fixtures, and joints, and potentially causing a burst line with immeasurable damages and cost.
When your water thermally expands, a water heater expansion tank prevents unwanted increases in pressure. Water expands by roughly 2% as it heats up from 50° F to 120° F.
You install the expansion tank down the line from the inlet valve that sends hot water into your home. The tank has two sections that are separated by a rubber valve. Water flows through the top portion, and there is pressurized air in the bottom.
It’s this air pressure that allows the tank to absorb the excess pressure from your water heater, which keeps it away from your home’s other systems.
If you have a “closed system,” meaning there is a backflow preventer or other device that won’t’ permit your water to flow back into the main water supply, thermal expansion will lead to significant pressure increases in your home’s plumbing system.
Not only should you have a thermal expansion tank under these circumstances, but some municipalities require it. Further, your water heater’s manufacturer might void your warranty if you have a closed system and fail to get this safeguard.
You don’t need a water heater expansion tank if you have a tankless water heater since there is no tank and no buildup of pressure. Likewise, if your home runs on an open water supply system, where excess water goes back into the municipal water supply, it won’t place any strain on your home’s plumbing system.