Raw sewage backup in downstairs shower when upstairs toilet is flushed
I live in a split level home (tri-level). When we flush the toilet on the top level, raw sewage backs up (belches up) into the shower on the bottom level. No other drains, toilets, etc, are affected. The washing machine, which is within 2 feet of the shower drains properly without any backup into the shower. I just had a Roto Rooter man come and check things out. He tried to snake out the lines but says he hit mud and that means that there is a break in the pipe behind the downstairs shower wall, probably where the copper pipe meets the cast iron pipe. He said that we will need to dig out the main line from the crawl space and replace it. I know nothing about plumbing, but it does not make sense to me that a broken pipe would cause the problems that we are having. Am I totally wrong? Should we get a second opinion? Any help would be GREATLY appreciated! Thanks!