How much does the knee clearance reduce for every 6 inches in height above the finished floor?

The correct response indicates that the knee clearance reduces by 1 inch for every 6 inches in height above the finished floor. This reduction is based on the established guidelines for plumbing design, which take into account ergonomics and safety within spaces where plumbing fixtures are installed.

When designing or installing fixtures such as sinks or workspaces, understanding knee clearance is critical to ensure comfort and accessibility for users. As the height of a fixture increases, the available knee space underneath it diminishes to accommodate the increased vertical space occupied by the fixture. This is essential for maintenance and usability, especially in residential and commercial environments.

The other options suggest larger reductions in clearance, which would not adhere to the standard practices in plumbing design. Such discrepancies could lead to uncomfortable or unfeasible installations that do not meet user needs or safety standards.