What is the function of an expansion tank in a hydronic system?

The primary function of an expansion tank in a hydronic system is to accommodate the expansion and contraction of water as it heats and cools. Water expands when heated and contracts when cooled, which can cause significant pressure fluctuations in a closed hydronic system.

The expansion tank absorbs the additional volume of water that results from the increased temperature, preventing excessive pressure build-up that could damage system components such as pipes and fittings. By providing a space for the expanded water to go, the expansion tank helps maintain stable system pressure and prevents the need for excess pressure relief measures.

This capability is crucial for the efficient and safe operation of the hydronic system, ensuring that the system functions without interruptions or leaks caused by pressure surges.