Roy using bad form unncessarily, massively and lazily full-quoted:

Yep, he is a stubborn one...I hope he likes dishes splattered with
raw sewage. It can happen.

I challenge you to explain how.

How sad it is that you think that a simple trap can prevent a sewage
backup into an upstream fixture, or even that that's what a trap is
for. Your knowledge of plumbing hydraulics and physics is pathetic.