Underground mains flow tests are required at what interval?

• A. Annually
• B. Every three years
• C. Every five years
• D. Only when repaired

Answer: (C)

Underground mains flow tests are done to verify that the primary water supply to the system can deliver enough water with adequate pressure and to catch gradual issues like pipe obstructions, leaks, or valve misconfigurations in the main. Because the underground main and the public supply don’t typically change rapidly, a longer interval is appropriate. A five-year interval provides a balance between catching longer-term deterioration and keeping the testing workload reasonable. Annual checks cover ongoing operational readiness and components, not the comprehensive flow test of the underground main. Waiting only after repairs would miss proactive detection of issues that could affect performance. So five years is the correct interval.