What is the function of a service valve in a cold water supply, and where should it be located?

• A. It isolates the building from the public supply for maintenance; located on the service line near the point of entry or at the main shutoff.
• B. It vents air from lines; located in the attic.
• C. It regulates pressure for each fixture; located at every fixture.
• D. It acts as a backflow preventer; located on the branch lines.

Answer: (C)

The function of a service valve is to completely isolate the building from the public water supply for maintenance or emergencies. It’s placed on the service line at the point where water enters the building, typically near the water meter or the main shutoff, so you have a single accessible point to shut off all indoor water.

Venting air, regulating pressure for each fixture, and backflow prevention are roles handled by other devices. Air vents handle air in the system, pressure regulators control pressure at specific points (not the main valve), and backflow preventers are separate devices placed where backflow risk exists, not as the general service shutoff.