Which of the following fixtures requires an independent isolation valve?

The correct choice highlights the requirement for an independent isolation valve for a dishwasher. This is critical because a dishwasher often connects to the home's plumbing system through a dedicated line, and having an isolation valve allows for easy maintenance and repairs without shutting off water to other parts of the house.

When servicing a dishwasher, it is essential to isolate it from the rest of the plumbing system to prevent flooding or leaks. The independent valve enables homeowners or technicians to turn off the water supply specifically to the dishwasher, facilitating safe and efficient repairs.

In contrast, other fixtures typically do not require their own isolation valves since they may be designed to share an isolation valve with another appliance or may not pose the same risks of leaks that require such isolation. For example, a washing machine might be tied into a shared line with an easily accessible valve, and many refrigerators are connected via existing plumbing that employs inline valves. While water heaters do have valves, they usually have a different operational setup focusing on regulating temperature and pressure rather than maintenance isolation specifically. Thus, the emphasis on the independent isolation valve for a dishwasher underscores both safety and convenience in plumbing management.