Predl’s polypropylene Wall Liners (Corprotect) protect the inner surface of the manhole riser from corrosion and water infiltration. Riser joints are capped with a PP strip and extrusion welded for a watertight seal. Predl Wall Liners are made of tough wastewater-resistant polypropylene. The low thermal shrinkage of polypropylene and 13mm anchors ensures a permanent and durable mechanical bond with the concrete. Wall Liners are produced for standard riser sections in 1′ (305mm), 2′ (610mm), 3′ (915mm) and 4′ (1.22M) heights for 42″ (1.07M), 48″ (1.22M), 54″ (1.37M), 60″ (1.52M) and 72″ (1.83M) diameter manholes according to ASTM C478 specifications. Predl Systems can manufacture custom sizes to virtually any dimension upon request.