Which plumbing fixture necessitates having an independent isolation valve?

A dishwasher necessitates having an independent isolation valve because it requires the ability to shut off the water supply for maintenance, repairs, or in the event of a leak without affecting other plumbing fixtures. This isolation is crucial for ensuring the safety and functionality of the plumbing system, as dishwashers can be prone to issues like clogs or malfunctions that may require immediate attention.

In contrast, while sillcocks, lavatories, and bathtubs connect to the plumbing system, they typically do not require their own separate isolation valves. Sillcocks often have shut-off valves installed at the source, which can control the water supply for multiple fixtures. Similarly, lavatories and bathtubs usually have access to their plumbing through central shut-off valves, allowing the entire system to be managed without the need for independent valves for each fixture. This design helps streamline plumbing configurations and maintenance procedures.