This type of control valve uses a circular disk inside a flat plate on top of the valve housing. When the valve is open, the disk is perpendicular to the surrounding plate. When the valve is closed, the disk is in line with the plate that surrounds it.

This type of control valve uses a circular disk inside a flat plate on top of the valve housing. When the valve is open, the disk is perpendicular to the surrounding plate. When the valve is closed, the disk is in line with the plate that surrounds it.

• A. Outside stem & yoke
• B. Post indicator valve
• C. Wall post indicator valve
• D. Post indicator valve assembly

Answer: (D)

The concept here is a valve position indicator built into a post indicator valve assembly. The circular disk inside a flat plate on top of the valve housing serves as the visual status indicator: when the valve is open, the disk sits perpendicular to the surrounding plate, and when the valve is closed, the disk aligns with the plate. This design lets anyone observing the post quickly determine whether the water main is open or shut, which is essential for firefighting operations and system isolation. That is why this option fits best: it specifically includes the indicator disk mechanism mounted on the valve assembly to show position. Other configurations describe different stem arrangements or wall-mounted indicators that don’t rely on this disk-in-plate visual cue.

The concept here is a valve position indicator built into a post indicator valve assembly. The circular disk inside a flat plate on top of the valve housing serves as the visual status indicator: when the valve is open, the disk sits perpendicular to the surrounding plate, and when the valve is closed, the disk aligns with the plate. This design lets anyone observing the post quickly determine whether the water main is open or shut, which is essential for firefighting operations and system isolation.

That is why this option fits best: it specifically includes the indicator disk mechanism mounted on the valve assembly to show position. Other configurations describe different stem arrangements or wall-mounted indicators that don’t rely on this disk-in-plate visual cue.