If a wastewater line enters a manhole invert more than 24 inches above the invert, which pipe type is recommended?

• A. Standard pipe
• B. J-drop pipe
• C. Slotted pipe
• D. Flexible hose

Answer: (B)

When the incoming sanitary line is significantly higher than the manhole invert, you need a feature that creates a controlled vertical drop into the manhole rather than a straight, abrupt entry. A J-drop pipe is designed for this situation. It provides a smooth, downward path from the higher line to the invert, which helps maintain gravity flow, reduces turbulence and splash, and prevents solids from piling up at a sharp entrance or at the rim.

Standard pipe would struggle to handle the large vertical difference without causing issues like solids hitting the floor or creating turbulence that can lead to blockages. Slotted pipe is meant for drainage that involves perforations and infiltration, not for conveying wastewater into a manhole. A flexible hose isn’t suitable for long-term wastewater service and wouldn’t provide the necessary rigidity or reliability. So the J-drop pipe is the best choice because it specifically accommodates a high-entry condition and promotes a stable, efficient flow into the manhole.