I am suspect of the tee connection above the tank as I believe CO can spill out. I have never seen one installed like this. Am I correct or is this OK.
The dirt leg is missing, because if it was installed correctly you wouldnt be able to open the filter door.
in ohio the furnace flue has to vent below the water heater flue. i have installed heating and air for 17 years.the way this is flued will cause water heater to back draft. needs fixed