Cured-in-Place Piping: The Question of External Point Repairs

Cured-in-place piping is a commonly used rehabilitation method for aging gravity sewer systems. In general, there is limited guidance on when external (open trench) point repairs are required in preparation for cured-in-place piping. The decision to make point repairs prior to installing cured-in-place piping is typically left to the engineer of record or other party reviewing the closed-circuit television (CCTV). This paper will examine the issues of determining when external point repairs may be appropriate prior to cured-in-place piping installation, and the potential impact of certain defects on long-term liner performance for small diameter (less than 24" gravity sewer) rehabilitation. Typical defects including holes, broken pipe, collapsed pipes, sags, and void spaces will be discussed. The use of external point repairs prior to installing a cured-in-place pipe is a balance between the severity of the defect, surrounding conditions, rehabilitation objectives, risks during installation, aesthetics of the final product, future maintenance and long-term performance.