Using triggers to then follow a specified path

Hi, I'm pretty new to unity and C# but I'm trying to make a simple ball rolling game. I've got a pipe in the level to go from lower to higher ground but I'm not sure how to go about getting the ball to move up the pipe. I can get the ball to do this upon hitting play but the pipe isn't the first thing in the game. I'm guessing that using triggers at either end of the pipe which set the ball to follow the bezier path should do it but I'm not sure how to go about this.

Any ideas or assistance on how to solve this issue would be greatly appreciated, thanks.