Wow, were to start
- I agree with the lack of trap and possible siphoning of sewer gas, unlikely but definitely possible. Being on the roof like that there would most likely be enough draft to keep that from being a real problem. Still a terrible installation.
- My guess is that the condensate drain is probably caulked into a drilled hole on the vent (typical crap work). Once the caulk seam fails water will probably enter the roof ... and then ...
- What is that built-up trough thing the drain is layed into? That looks like another roof seal failure point. Water must accumulate in there everytime it rains.
- It looks like a flat roof. Around here the hvac guys either: just let the condensate run onto the roof; or run the drain over to the gutter.

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Accurate Inspections & Consulting, Inc.
773/844-4AIC
Markus Keller