Which of the following statements about infiltration in sewer systems is true?

• A. Improper closed circuit TV operation.
• B. Poor ventilation.
• C. Cracked pipes.
• D. All of the above.

Answer: (C)

Infiltration is water from the surrounding groundwater seeping into the sewer system through defects in the pipes and joints. Cracked pipes provide a direct pathway for that groundwater to enter, especially when groundwater levels are high or during wet weather, making cracked pipes the true statement about infiltration.

Improper closed circuit TV operation describes how we inspect pipes, not a source of groundwater entering the system. Poor ventilation concerns air movement and gas buildup in the sewer, not infiltration of groundwater. Therefore, “all of the above” isn’t correct because the other two items aren’t sources of infiltration.