I have a small PVC hoop house that I built last winter and plan on using again this winter. I found out first hand, then read about it later on, that the plastic used for greenhouses will react with PVC and turn white. Since I've already invested in the PVC, and it's a much cheaper alternative to metal pipe, I'm trying to come up with a way to isolate the plastic from touching the PVC.
The options I've come up with so far are to use some type of tape (felt, electrical, clear duct tape etc.) and apply it to the outside of the hoops where they come in contact with the plastic. My purlins are attached on the inside of the hoops so I don't need to worry about them. The felt shouldn't react since I've seen this sold on greenhouse supply websites for just this reason, but what about the tape? Are there any other low-cost options I'm missing?
The design is changing a bit the second time around, but this is what it looks like from the inside. As you can see very little PVC actually comes into contact with the plastic covering. The plastic I used was from Green-Tek which I think is really Dura-Film Super 4 from AT Films and it's what I plan on using again this year.