If a pipe disinfection test fails to meet minimum standards during the first test, what should be done?

• A. the water should be tested again
• B. discontinue testing and accept results
• C. increase disinfectant concentration and retest
• D. replace pipe and retest all sections

Answer: (A)

When a pipe disinfection test fails to meet minimum standards on the first try, the next step is to re-test the water. This verifies whether the failure is real or just a sampling or lab anomaly, since issues like improper sampling technique, insufficient contact time, or lab variability can produce a false fail. Re-testing confirms the result before making any corrective changes. Jumping straight to increasing disinfectant, replacing pipe, or accepting the failed result could lead to unnecessary changes or unsafe decisions, so the prudent first move is to re-test to establish a reliable result.