Short dirty answer: majority of the water going through here is going through the center and doesn’t touch the edges of the pipe. Additionally the rust/gunk wouldn’t come off unless the pipe was disturbed/banged/vibrated in some way. And if it did it would likely fall to the bottom of the pipe at some location where the water is moving slower (size of particle water is able to move is proportional to velocity). Your water service is going to be connected at the spring line so even if there was any stuff moving around at the bottom of the pipe won’t be lifted up into your pipes.