Original sewers were designed with a certain slope that ran on a predictable flow of water. They flushed themselves for the most part. The low flows don’t wash out the tubes.
http://www.sfgate.com/bayarea/matier-ross/article/Low-flow-toilets-cause-a-stink-in-SF-2457645.php
It’s not a simple matter of simply upgrading. It was a politically caused problem. Feel good about low flow toilets while the entire system backs up. This is like the ethanol mandates ruining engines. A politician gets bought off, mandates we all put that garbage in our automobiles, and it ruins the engine.
Yes, a bit off topic from wipes, but if there was the back flow of the water to push them through this wouldn’t be much of an issue.
I think you’re mixing apples and oranges. See post 36, regarding treatment plants.