What divides a pressurized expansion tank?

A pressurized expansion tank is designed to manage the expansion of water as it heats up in a closed-loop system, such as a hot water heating system. The correct choice, which is a flexible diaphragm, effectively separates the tank into two distinct chambers. One side of the diaphragm is filled with air and pressurized, while the other side contains water from the heating system.

As water heats up, it expands, and the excess pressure created is absorbed by the flexible diaphragm. This design helps to maintain system pressure and prevent issues such as water hammer or excessive pressure in the pipes, which could lead to leaks or failures. The diaphragm allows for a responsive movement that adjusts to changes in pressure without allowing water and air to mix.

The other options, such as a solid wall, rigid frame, or metal cover, do not serve the purpose of accommodating the expansion of the water. A solid wall would restrict movement and negate the function of the expansion tank, while a rigid frame would not provide the necessary flexibility to absorb pressure changes. A metal cover is simply an outer protective component and does not play a role in the internal function of the tank. Thus, a flexible diaphragm is essential for the effective operation of a pressurized expansion tank.