Welcome to the Forum, Glenn:
I don't know if the folks here can stand 2 Glenn's, but we will have to give it a try.
Your steam pressure releif valve should come directly off the steam generator within 3" of the generator, extend outside with a fall for drainage, and to within 4" of the ground. Steam can build a tremedous amount of pressure and, if it exceeds the municipal water pressure, it will back up in the service pipe unless there is a backflow preventer. Many municipalities require a backflow preventer at the meter, so that any pressure or contamination on your side can't affect the whole neighborhood.
Having the releif line run to the ground will prevent anyone from getting scalded if it does pop off. Keep in mind; when water changes to steam it expands to 17 times its original size. You can see how that would cause a lot of pressure.
Glenn (the Kentucky one)