Which backflow preventer is commonly used on sprinkler systems to protect potable water?

• A. Double-check valve (DCV) assemblies
• B. Gate valves
• C. Ball valves
• D. Strainers

Answer: (A)

Backflow prevention is about keeping irrigation water from flowing back into the potable water supply. For sprinkler systems, the device you’ll most often see protecting the drinking water is the double-check valve assembly. It uses two check valves in series with a small relief passage that activates if water starts to flow backward, stopping any reverse flow into the supply. This setup is well suited for the typical, lower-hazard cross-connections found in most irrigation systems, and it’s relatively simple, reliable, and cost-effective to install and test (test cocks let you verify proper operation).

Shut-off valves like gate or ball valves are just isolation devices; they don’t prevent backflow themselves, they only stop flow in one direction when closed. A strainer’s job is to remove debris, not to stop reverse flow. So while those components have important roles in a system, they don’t provide the backflow protection required for potable water, which is why the double-check valve assembly is the commonly used choice for sprinkler backflow protection.