Which of the following is important for the placement of an expansion tank?

The placement of an expansion tank is critical for its proper functioning, and one of the key requirements is that it should hang downwards. This downward orientation helps ensure that the tank can effectively manage water pressure and accommodate the expansion of water when it is heated. When water heats up, it expands, and the expansion tank serves as a cushion to absorb this extra volume, preventing excessive pressure in the plumbing system.

Positioning the expansion tank below the plumbing lines takes advantage of gravity, allowing for optimal water flow and pressure management. This arrangement also reduces the likelihood of air pockets forming within the tank, which can hinder its performance. Additionally, a downward-facing position enhances the tank's ability to release air trapped within the system, improving overall water circulation.

Other considerations, such as convenience of access or visibility, while practical, do not directly impact the function of the expansion tank in the same critical way that its orientation does. Adjustability might be useful for installation purposes but is not a fundamental requirement for the operation of the expansion tank. Therefore, the downward placement is essential to ensure the effective performance of the system it is part of.