"Speedy Jim" wrote in message
...

Crawl space means no floor drains, as there would be in
a basement. Right? So, all the fixtures are well above
grade level.

In that case, I would say there is zero likelihood of
backup out of toilets/sinks due to stoppage/flooding of
the city sewer.

Isn't it possible for a neighbor to throw something in the toilet that
eventually clogs the city sewer line? If this happens, then subsequent
flushing or use of water would cause a backup. Or is the city sewer line so
large that nothing passing through a toilet could possible get stuck there?

If there was a stoppage, either in the sewer or in your
lateral connection (tree roots) AND you flushed a toilet,
then it would/could backup within your house.