How does a check valve differ from a backflow preventer, and when is a check valve adequate?

• A. A check valve prevents flow reversal; a backflow preventer protects against back-siphonage and backpressure.
• B. A check valve prevents flow reversal; a backflow preventer protects against back-siphonage and backpressure; a check valve is adequate for simple downstream isolation where no cross-connection risk exists.
• C. A check valve allows reverse flow under pressure.
• D. A check valve is a type of regulator.

Answer: (B)

A check valve is a one-way device that lets water flow in the intended direction and closes to prevent any reverse flow. It provides simple downstream isolation but does not protect against backflow caused by cross-connections, back-siphonage, or backpressure scenarios. A backflow preventer is designed to guard against both back-siphonage and backpressure, stopping contaminated water from entering the potable supply through cross-connections. Because of this, backflow preventers are used where there is a potential cross-connection or other backflow risk and they are typically tested and certified to meet code requirements. A check valve is adequate when there is no cross-connection risk and you simply need to prevent downstream water from flowing back into the supply, such as isolating a section of piping or equipment that cannot create a backflow hazard. If there’s any chance of cross-connection or backpressure, a backflow preventer is the appropriate choice.