How should expansion tanks be properly bled?

Properly bleeding expansion tanks is essential to maintain their functionality and ensure the efficient operation of a heating or cooling system. The correct procedure involves releasing air from the top until all air is removed. This is because air tends to accumulate at the highest point in a closed system. If air pockets are present, they can hinder the expansion tank's ability to absorb excess pressure or allow for the thermal expansion of water, leading to potential system failures.

Bleeding from the top allows you to effectively remove air without introducing colder water that could be at the bottom of the tank, which is essential for maintaining optimal temperatures and preventing cold spots. Additionally, if air remains in the tank, it can lead to water hammer, noise issues, and ultimately reduced system efficiency.

Choosing to bleed from the bottom may inadvertently trap air at the top, and utilizing a pressure gauge could assist in monitoring system pressure but does not address the presence of air directly. Maintaining the functionality of an expansion tank requires that it is fully bled of air, which can only be achieved effectively by starting at the top.