The American Water Works Assn. (AWWA, Denver, Colo.) divides cured-in-place pipe (CIPP) into four classes based on three primary distinctions in terms of structural function:
Class I: Nonstructural liners; act only as corrosion barriers.
Class II and Class III: Semistructural liners; designed to cover small holes or gaps in the host pipe.
Class IV: Fully structural liners; will carry the full internal pressure without support from the host pipe.