I will address the last statement in John's post first. You are right, that is left unaddressed. I only addressed the formulation.

Now to address the remainder. I could be wrong for any brand other than CertainTeed. However, I spent 4 years as the Quality and Production Manager at a CertainTeed pipe plant. We used our approved NSF formulation for both pipe products. We always scheduled PVC first, then conduit through the same extrusion die. The entire change procedure was to add the colorant and change the printer.

Darrel Hood
DILIGENT PROPERTY SERVICES
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