What technique involves inserting an internal lining to cover multiple leaks in a pipe?

• A. Slip-lining
• B. Backfill
• C. PVC liner
• D. Horizontal breaks

Answer: (A)

This question tests understanding of trenchless pipe repair that fixes leaks from the inside. Slip-lining involves inserting a new pipe inside the existing damaged pipe. The interior of the old pipe is effectively lined by the new liner, so leaks along a length are covered and the flow is restored without digging up the line. It’s especially useful when there are multiple leaks along the same run, because one interior liner can seal many weaknesses at once and create a continuous, smoother interior surface. After placement, the annular space is sealed to keep the liner in place and prevent movement.

Backfill is about replacing soil around a repaired trench and does not provide an interior lining. A PVC liner refers to the material used for lining in some methods, but the described technique—placing a liner inside the pipe to span multiple leaks—fits slip-lining best. Horizontal breaks describe the damage pattern, not the repair method.