During Lamping, what fraction of the pipe circle should be observed vertically and horizontally?

• A. One fourth
• B. Three fourths
• C. Half
• D. Full circle

Answer: (B)

Lamping is a quick visual check of the pipe interior by shining a light into the sewer and inspecting the wall surfaces for defects. Because the light only reveals a portion of the wall at a time, you scan the circumference by moving and angling the lamp. You should be able to observe about three quarters of the pipe circle in both vertical and horizontal directions. This level of coverage gives a thorough view of the walls—enough to spot cracks, corrosion, or buildup—without being impractical to perform in a single pass. Observing only a small portion, like a quarter, would leave most of the surface unseen, while aiming for a full circle in one position isn’t feasible due to lighting and geometry.