What is the purpose of a check valve on a cold water line feeding a storage tank, and how does it relate to backflow prevention?

• A. Prevents reverse flow into the main supply from the storage tank, reducing backflow risk and maintaining one-way flow.
• B. Regulates pressure to the storage tank; ensures high pressure.
• C. Serves as a relief valve for tank overpressure.
• D. Used to drain the tank during maintenance.

Answer: (A)

A check valve on the cold water line feeding a storage tank is there to prevent backflow into the main supply. It allows water to flow into the tank, but closes if pressure on the tank side tries to push water back toward the supply. This one-way action is a fundamental way to stop backflow and protect the potable water supply from contamination or siphonage.

Backflow prevention is about keeping the supply from being drawn backward through a connection. A check valve provides simple, automatic protection by sealing off reverse flow, though higher-risk situations may require additional devices like air gaps or other backflow preventers.

This device isn’t meant to regulate pressure or ensure high pressure, so it doesn’t function as a pressure regulator. It isn’t a relief valve for relieving tank overpressure, and it isn’t used to drain the tank during maintenance. Those roles belong to other components.