CPVC 3/4" Union. CPVC is a Scheduled Pipe designed for both a hot and cold water. CPVC is ideally suited for temperatures up to 200 Â°F (90 Â°C) and corrosive water applications. CPVC is far more ductile than PVC and it's more resistant to crushing. CPVC and its fittings must be solvent glued together, the glue and solvent are designed to create a seal that is leak proof and durable like the CPVC pipe itself. This CPVC 3/4" Union is used to join lengths of pipe together. The threaded nut allows you to tighten the fitting without twisting the already existing pipes.