It would be difficult to explain what this configuration looked like when I first saw it. There were a multiplicity of problems, all identified on my original inspection report, and the seller agreed to many repairs. This is what we saw when we returned to what is apparently thought to be the Bestway* to do it.
The list of what was wrong to begin with was enormous. These repairs are as you see them.
The water heater exhaust hood is still disconnected where it exits the unit.
The previously single-walled furnace vent is now a new double-walled vent, but still angled downward.
It exits the wall on the left, but we can't see if it is still touching the wood framing. But it is still horizontal inside that chase above the water heater, coming from 15' to the left. It hooks downward at a dramatic angle to turn again as it extends to the chimney.
It no longer loosely enters the chimney (on the right) as it is attractively glued with polyfoam. We see polyfoam in so many places used in so many ways! It is as ubiquitous as duct tape!
It is time for thermal images!
The furnace is on the ground in the crawl space to the left of the first image above. The vent goes up and inside the chase, after it makes many turns. It is a single-walled vent inside that chase! It touches wood framing, drywall and the AC line seen in the photograph above. That AC line follows that furnace vent along the entirety of the 15' chase. It can't be in a good condition. The middle image above is similar to the photograph at the top. The hottest spot, as demonstrated by the white color, is just to the left of the left tube connecting to the top of the water heater. That spot is 183F! The corner, where all the tubing makes many turns and goes downward, is 177F. Imagine how hot it is inside the chase! The right image shows where the two tubes enter the chimney.
I think that when they connected the double-walled vent to what existed before, they disconnected things inside the chase, accounting for the high temperatures. Heat doesn't vent downward well! It clogs, as you can see, and builds up. I don't know what is going on at the chimney connection. I suspect the wide gaps between the vent and brick work are still there behind the metal plate. It still lacks a clean out port.
* Bestway Construction asked to have me call them with anything that might still be wrong or not to code.
I'm sorry, a home inspector's purview is not to tell a supposedly licensed "construction" company if their work is wrong or not to code... Any company worth it's salt, um, soy sauce already knows that!
My recommendation: Hire professionals to do work when repairs need to be done! And remember, heat should be vented upward! It isn't heat that flows downhill...