2 Vents into 1

[ryoung7 (ROBERT YOUNG, CMI)]

@rjohnson11

The connection is not an issue, the way its connected is. The “Y” fitting should be turned so that the hot water tank vent is above the furnace connection point. If the “Y” fitting were turned a min of 75 degrees clockwise, it would pass code.

Two appliances connected into single vent

Here,s a post from Febuary of this year.
I think you should do some homework on this one.