Flue angle

This flue goes down then back up. Should I report this in my report?

Definitely! Also inform anyone that may be living there.

Heck YES put it in your report as WRONG

Brian, some of the defects we find, as professional home inspectors, can kill people.

Your picture, here, shows an example of that.

No one is perfect but please consider additional education before harming yourself or others.

http://www.nachi.org/forum/attachments/f20/33910d1261244504t-flue-angle-056.jpg