Hello everyone. This is my first post here, but your advice helped me before, and I'd appreciate any insight re this problem.

We have two-story condo unit with attic, and natural gas water heater and central heat and AC system. Just recently when AC was running and water heater kicked in, we felt a strong smell of exhaust and CO alarm went off.

My HVAC contractor, whom I trust, while trying to figure out the problem, discovered that the flue pipe in the attic came apart at the "elbow" and was leaking exhaust. He shut off the heater, and we called the condo management.

Condo management office sent a roofing contractor who "fixed" the gap by putting screws and taping it over with aluminum tape because they did not have an appropriate size/type elbow to replace the broken one.

My HVAC contractor refuses now to turn the water heater back on because he considers this tape "fix" unsafe for a B vent. On the other hand, he does not want to take care of replacing the elbow himself saying he is not a chimney expert and cannot guarantee safety.

Don't know what to do now, though I feel that I agree with my guy. But maybe he's making too much a deal out of it, and taping over the gap is perfectly acceptable?
Or do I need to find a chimney expert to replace the broken elbow if we can get it from the original manufacturer?

The house is some 30 years old. I'd think the pipes/vents are original.

Thank you for any insight you can offer. The picture is of the broken part before it was "fixed" yesterday.