This is the first time I have seen this connection of the flue vent cap to the water heater. The tabs were spread out and the cap was installed flush to the water heater. A downward facing open Tee was installed inline. (likely to induce drafting) Is there anything wrong with this? I did recommend further evaluation.
Anytime you see something like that you have to look for the appliance manual on the side of the W.H. It should be there…it better be there The MFG install instructions will tell you. Then the AH can modify it… MFG first.
I bet the flue above the W.H. was in the “way” so a a little field modification was in order…
The only time that you should see this kind of connection would be on a mobile home water heater. Otherwise I know of no manufaturer that would allow this. I’ve installed at least two-five water heaters per week for the last ten years using various manufactures and have not come across this type of instalation.
Expand- I do have limited experience with mobile home water heaters because the companies I worked for usually did not work on mobile homes. The reason for a sealed vent is because mobile home water heaters are usually in confined spaces with bad access to them. The confined space does not allow enough fresh air to get to the chimney for proper updraft. I believe the fresh air comes from below. The gas one’s I replaced were replaced with electric water heaters. I hope this helps.
Someone who works on mobile homes would be better qualified to answer this.