Boiler flue slope

In the pics attached you can see there is upward slope with the flue then there is a slope downward to the chimney opening. Is this slight drop enough for concern that others would point out?


Yes, and it appears to be a very simple fix.

Agree just twist the elbows to allow for continuous minimum 1/4" per foot rise from source to exhaust. If it is too flat across the horizontal run shorten the stack slightly. To maintain the 1/4"/ft.