Respond to a drinking-water chlorine residual miss

Practice the 40 CFR 141 / primacy-agency residual order. Water is not declared safe, and a boil-water notice is not issued, until a confirming grab, restore-and-flush, resample, and the primacy path are followed.

1. Confirm the residual with a second grab and a calibrated kit.
2. Check feed equipment.
3. Check tanks and recent distribution changes.
4. Increase or restore disinfection only as the SOP allows.
5. Flush the affected mains.
6. Resample at the required locations.
7. Notify the primacy agency if the residual or repeat sample meets a reporting trigger.
8. Issue a boil-water or do-not-drink notice only when that authority directs it.