Most toilet papers are fine, although some systems struggle with Costco's stuff. Toilet paper is designed to break apart in water. That said, you shouldn't flush any other products. Paper towels don't break down the same way, and wipes will almost certainly cause damage, even if they are marketed as flushable!!
Waterdoc
joined 10 months ago
Sadly this is pretty common. Here are some nasty pictures from a recent one in greater Vancouver.