Expansion Tank

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Expansion Tank

What is Expansion Tank?

An expansion tank is a plumbing or HVAC component that absorbs pressure changes caused by thermal expansion in closed systems.

Description

An expansion tank is a device installed in closed plumbing or hydronic heating systems to absorb excess pressure created when water heats and expands. Without an expansion tank, increased pressure can damage pipes, valves, and fixtures or trigger pressure relief valves.

In construction and mechanical systems, expansion tanks are commonly used in domestic hot water systems, boilers, and radiant heating systems. They typically consist of a steel tank with an internal bladder or diaphragm that separates water from compressed air, allowing pressure fluctuations to be safely absorbed.

Proper sizing and placement of an expansion tank are critical for system performance and code compliance. Tanks must be matched to system volume, operating temperature, and pressure range. When correctly installed, expansion tanks help extend system life, reduce maintenance issues, and ensure safe operation.

FAQs

  • What is an expansion tank used for?

    It absorbs pressure increases caused by heated water in closed systems.

  • Where is an expansion tank installed?

    It is typically installed near water heaters, boilers, or hydronic heating equipment.

  • Are expansion tanks required by building code?

    Many codes require expansion tanks on closed hot water systems.

  • What happens if an expansion tank fails?

    System pressure can rise, leading to leaks or activation of pressure relief valves.

  • Do expansion tanks require maintenance?

    Yes, periodic checks of air pressure and bladder condition are recommended.

Fun Fact

Expansion tanks help protect systems silently—most homeowners never notice them unless there’s a pressure problem.

CSI Code

22 05 16

NAHB Code

3310