Water heater vent size increase and penetration

[Jon mackay]

This water heater vent connects to a larger flue pipe in the attic. Is this acceptable? I was thinking that it may interfere with proper venting.

Also this ceiling penetration looks like a wall thimble. Are these allowed in ceilings?

[Philip]

Looks like a classic spillage. The house has a lot of fresh air coming in or their might be bodies.

[Jon mackay]

I don't believe there is any spillage, it appears that the pipe passes directly through the penetration.