TOPIC: what do you think of this water heater venting configuration?

Yup, I think that's what we would need to know to make a good decision.  But from what I can tell just from what I see, I'm not so sure its actually breaking any rules for venting.  I could be forgetting something though.  I didn't look it up.  Normally if I had found it on an inspection I would be asking you guys of talking to my plumber friend.

The angle wont show it, but yes, it is joining the hvac vent and then exiting through the wall.
in my report, i recommended that an HVAC tech perform maintenance and evaluate it at that time. I sugested that it is not the typical configuration, but i did test with a co meter  for safetys sake.

I know one issue is that to ensure a positive draft, it should rise at one-quarter inch per foot. If indeed that is not a tee. I'm not sure if there are any other issues without looking it up.

I know one issue is that to ensure a positive draft, it should rise at one-quarter inch per foot. If indeed that is not a tee. I'm not sure if there are any other issues without looking it up.

You are right, but that is a minimum standard.  It can go straight up if needed.  It may not meet that min standard right where it joins the T though.

Here the furnace and water heater vents must be separated and enter the chimney flue or exhaust stack at different points.  Couldn't tell from the picture, but how far is that draft hood off the top of the unit?

improper install no separation of venting improper sealing at joints