Smoke testing is typically performed under what hydrological condition?

• A. When groundwater is low
• B. After heavy rainfall
• C. During drought
• D. During flood

Answer: (A)

Smoke testing works best when the ground and sewer are dry, with groundwater at a low level. When the system isn’t flooded with groundwater, the smoke can fill the pipes and rise through any defects or improper connections, making leaks visible at manholes, vents, or building connections. If groundwater is high or wet weather is occurring, water in the soil and in the sewer can fill cracks and joints, preventing the smoke from entering those voids or carrying it away too quickly, which hides leaks and makes results unreliable. Heavy rainfall or flooding adds moisture that can obscure visibility and cause false indications. Dry, low-groundwater conditions give the clearest, most reliable view of where leaks or cross-connections exist, so testing during these times is preferred.