Which device is used to separate sections of the mainline to isolate downstream segments for repair?

• A. Mainline isolation valve
• B. Winterization/start-up
• C. Wire path isolation
• D. Sleeving

Answer: (A)

Isolating a section of the mainline for repair relies on a valve designed to stop flow in the main line. The mainline isolation valve is placed on the line and can be closed to prevent water from reaching downstream segments while repairs are made, allowing maintenance without draining or disrupting the entire system. The other options don’t fit this purpose: winterization/start-up relates to seasonal protection and system preparation, not isolating sections; wire path isolation isn’t a standard device for controlling water flow; sleeving is about protecting lines or cables, not shutting off flow.