Last fall, I planted a Japanese Tree Lilac in my front lawn...it is
currently 7 feet high and is supposed to get between 15-25 feet. However
being a total newbie, I didn't consider where my sewer line is and I think I
may have planted the tree nearly on top of it.

Since its only an ornamental tree, should I be worried and possibly remove
or move the tree?

Home is 50 years old...neighbor's sewer just backed up the other week.

Thanks,
Mike