I am going to bury a 4' diameter culvert in the ground to contain my pressure tank and well controls. Presently there are no buildings on site but I want to get the well going and get the landscaping started, ie trees, shrubs, and grass. The culvert is 7' long and will be set on a deck built with treated 2" x 6"'s buried to 6'6". It will have heat as the frost level is about 5 feet down.

I am going to feed my House, irrigation, and RV hookup with 1" poly pipe. I am looking at the need for some flexibility inside the culvert connecting the feeder and incoming poly pipe to the tank and associated hardware for maintenance and repairs. I am thinking about using galvanized pipe unions in all incoming and exiting runs. Is there other ideas out there to give some "flex" and ease of movement with the poly as the room inside the culvert will be quite tight? Once inside the culvert can I change to some sort of rubber or softer plastic tubing?