"I asked my supplier and they suggested using HDPE inserts for polypro. Because polypro on polypro causes quite a friction because it's the same material, apparently HDPE slips in much better. I've never tried the pliers idea,…"
"I'm having the same issue. The inserts(smaller pieces of tubing) work with my 3/4 tubing, but the 5/8s have NO CHANCE of fitting. At all. Too much friction--i'm wondering if it's an impurity in the plastic or if…"
"Yeah I'm pretty anal about my tapes. For this reason I never use more than one foil-based tape, because they totally have a mind of their own and trying to layer them symmetrically has proven to be impossible--for me at least. …"
"Also, polypro is one of the top recycled products. It's resin number 5, on margarine containers and lots of catering products that require highly heat-resistant plastics. I think this goes for tubing too--I know a couple irrigation…"
"So you mentioned using pure materials--does this mean you used homogenous polypro? Homo PP has higher crystallinity, whereas copopolymer PP, made with ethylene, tends to have less tolerance for heat, etc--though it is more flexible. …"