Remodeling an unfinished basement. Had to open the concrete floor to move the shower and toilet lines. The 4" cast was rotted out. Ended up replacing 20' before we finally tied into good pipe. At the same time, I'm remodeling and moving two toilets in the bathrooms upstairs. I wanted to update with two new higher performance 1.6 gpf toilets. My plumber said if it was him, he'd stay with my old 5 gpf toilets. The problem is, it's 90' from these toilets to the sewer main. Also, the remaining cast in the ground isn't that smooth. He advised if the new toilets can't push the waste all the way to the main without having to do multiple flushes you've wasted a bunch of money and gained nothing. He said you had zero issues with the old toilets for all these years. He suggested buying a pair of cheap toilets to pass inspection, and then clean up and reinstall the original toilets. I'd still like to do a couple high performance toilets, but don't want to waste the money if he's right. Sorry for the long first post, but I'd really like some experts second opinions. Thanks...