I have my upstairs plumbing hooked up to my down stairs plumbing and then it goes through a back flow preventor. Twice in the last four months thAt preventor has stuck open with toilet paper and backed up into the basement. The plumber that did my house said that that was code when he did my house in 2001 and that it has since changed to only having that back flow on the down stairs plumbing. I have some plumers tell me "off the record" to take that flow preventor off and my problem is solved yet if we have a sewer backup it will come in my house. I have another plumber that wants to redo my upstirs plumbing and take it off the back flow preventor.
this would make it up to current code.
I don't know what to do.