Under what condition is a thermal expansion tank required?

A thermal expansion tank is required for a closed loop system. In a closed loop plumbing system, water is heated and expands as its temperature increases. This expansion increases the pressure in the pipes, which can lead to various issues, including premature wear on plumbing fixtures, increased risk of leaks, and potential failure of pressure relief valves.

The primary function of a thermal expansion tank is to absorb this excess pressure caused by the expanding water, allowing the system to maintain safe operating conditions. By doing so, it protects the integrity of the plumbing system and ensures that water is delivered efficiently.

In contrast, in an open loop system, water can flow freely and is not confined, so there is no buildup of pressure from thermal expansion. Similarly, the installation of a thermal expansion tank is not required simply because the water heater is new, nor is it necessary for every water heater installation, especially if the system is designed in such a way that accommodates the expansion without the need for additional tanks.