Liners are installed in sewers to correct problems caused by

• A. Infiltration
• B. Grade alignment
• C. Grease
• D. Grit

Answer: (A)

Liners are used to restore the inner surface of an existing sewer pipe and seal leaks, cracks, and joints so water cannot seep into the pipe. This directly addresses infiltration, which is groundwater or rainwater entering the sewer system through those cracks and joints. Reducing infiltration helps lower the flow that the sewer must carry, improving hydraulics and reducing overflows during wet weather.

Grade alignment, grease, and grit are different problems. Grade alignment refers to the slope or directional alignment of the pipe, which lining doesn’t correct; major grade issues typically require regrading or replacing the pipe. Grease involves fatty deposits that stick to the pipe walls and cause blockages, not leaks that liners fix. Grit are abrasive solids that wear pipes and trap sediments, which again isn’t solved by adding a liner.