This water heater was installed 7 months ago by a local and well known Dayton plumbing company.
They must have sent their least trained installer with a big box of bits and told him to use up everything in the box!
Issue #1: The flue pipe must have a continuous upward slope.
Issue #2: The furnace should not connect to the bottom of a “T connector”
Issue #3: is what you cannot see, the brick lined chimney has not had a liner installed.
What looks OK is often a very expensive repair.