How large in diameter is the coil on the end of the large sewer snakes they
use to clear the main sewer lines, when necessary?

Just wondering. We had to get a cleanout installed, and the reinforced
concrete pipe they put in place is about two feet long, with a hole in the
cast iron pipe it sets on that is only a couple inches across. I am wanting
to build a guide to use for pointing the snake in the desired direction, so
no guessing is needed to figure out which way it is headed. Thinking that
might come in handy if the cleanout pipe is full of stuff from the cloggged
line.

Thanks,

Dave