I've been installing for years by trenching. I've got several jobs lined up and am really close to buying a vibe plow. I've got a good idea on how to go about things but naturally there are questions. I'll be using pvc. For instance when it comes to tees and 90's. How do you avoid hitting the 1st line you have installed? I realize you can slide the pipe to some degree. I'll probably use glue on saddle T's with swing pipe unless you have a better idea. Do you pre trench the spots where heads will go if the ground is hard?