In systems where the sole water supply is through backflow preventer and/or PRVs, the main drain test downstream of the device is conducted on what basis?

In systems where the sole water supply is through backflow preventer and/or PRVs, the main drain test downstream of the device is conducted on what basis?

• A. Daily
• B. Quarterly
• C. Weekly
• D. Annually

Answer: (B)

The key idea is that the main drain test downstream of a backflow preventer or PRV checks that the device is actually preventing flow to the downstream side and is sealing properly. When this assembly is the sole source of water for the system, any leakage or failure to isolate the downstream side can immediately disrupt service, so the test is done more frequently to catch problems early. Conducting the main drain test on a quarterly basis provides regular verification that the device continues to seal and isolate the downstream line, catching wear, debris, or seating issues before they become outages. Annual tests may still occur for overall device function, but in sole-supply setups the quarterly drain test is the standard cadence.

The key idea is that the main drain test downstream of a backflow preventer or PRV checks that the device is actually preventing flow to the downstream side and is sealing properly. When this assembly is the sole source of water for the system, any leakage or failure to isolate the downstream side can immediately disrupt service, so the test is done more frequently to catch problems early. Conducting the main drain test on a quarterly basis provides regular verification that the device continues to seal and isolate the downstream line, catching wear, debris, or seating issues before they become outages. Annual tests may still occur for overall device function, but in sole-supply setups the quarterly drain test is the standard cadence.