What Is the Purpose of an Expansion Tank For Your Hot Water Tank?

the Purpose of an Expansion Tank For Your Hot Water Tank

What Is the Purpose of an Expansion Tank For Your Hot Water Tank?

Because water will expand when heated, the excess pressure inside the water heater tank needs to be released. In the past, the expanding water in the tank would simply drain back out into the municipal water supply where it came from. Today, the water main is designed to prevent the backwards release of pressure, known as backflow, by employing a check valve. The check valve prevents waste water from inside the house returning to the water supply where it can contaminate the supply of fresh water.

A hot water tank expansion tank is another small tank that is attached to the water supply pipe of the water heater. The expansion tank is designed to handle the thermal expansion of water as it heats up in the water heater, preventing excessive water pressure. If water pressure gets to high it can damage valves in plumbing fixtures, joints in supply pipes and the water heater itself. Expanding water from the water heater flows into the expansion tank, relieving water pressure in the system. So the expansion tank on your hot water tank is important. Read on to learn more.

What if my water heater doesn’t have an expansion tank?

Most homes that have a check valve on the water main do not have an expansion tank, since it wasn’t required until recently. This may or may not cause excessive pressure buildup, depending on the specific design of the plumbing in the house.

If you are noticing that washers in plumbing fixtures are deteriorating rapidly, or water is dripping from the relief valve on the water heater, it may be wise to add an expansion tank. It can be low-cost insurance against more costly damage to your home’s plumbing system.

Do I need an expansion tank installed?

An expansion tank is always highly recommended if you have a ‘closed-loop system’ caused by any kind of check valve or pressure regulating valve installed on your house’s water supply line.

A common analogy compares having high water pressure in your home to having high blood pressure. It usually doesn’t have immediate negative consequences. However, the long-term wear and tear of this excess pressure can reduce the life expectancy of everything on your plumbing system.

If you have excess pressure over 80 P.S.I. supplied to your home by the city water supply, an expansion tank does nothing to correct this. That’s the job of the pressure reducing valve (PRV). When the pressure supplied to your home is at the proper level between 40 and 80 P.S.I. and you have a PRV or check valve, that’s where the thermal expansion tank comes in. It protects against the constant fluctuation of high pressure caused by thermal expansion upon a closed-loop system.

Learn more about expansion tanks and hot water tanks by calling a professional.

Depending on where you live, an expansion tank might be required by the city regardless of the water pressure in order to pass plumbing inspections – such as you would get upon the installation of a new water heater. For instance, in British Columbia a PRV and expansion tank are currently required on all new homes.

Check with your city’s plumbing inspector to be sure of the applicable plumbing codes in your area. Or call Murrayville Plumbing & Heating to have one installed. We install gas hot water tanks and electric water heaters anywhere in the Fraser Valley and Lower Mainland. We even install tankless water heaters if you want to have on demand water system. Call us today 778.888.6451 we have a 24 hour emergency team that can help with any leak, hot water tank, plumbing, heating or gas fitting issue you have.

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