Where are isolation valves most commonly located in a cold water distribution system?

• A. At fixtures or branch lines serving individual rooms or appliances.
• B. Inside the water meter box.
• C. Only on the main supply to the building.
• D. On the hot water supply only.

Answer: (D)

Isolation valves are placed close to fixtures or branch lines so you can shut off just that portion of the cold-water system for repairs or maintenance without draining the entire building. This local placement is the most practical and common setup because it minimizes water waste, speeds up work, and makes testing or replacing a single fixture easy. While you might find shutoffs inside a meter box or at the main supply, those locations are used for service or whole-building shutoffs, not for isolating individual rooms or appliances. Valves for the hot water system serve a different part of the plumbing and aren’t part of the cold-water distribution isolation pattern.