Ok, just to provide a bit of levity; they say a picture paints a thousand words and I’m posting this pic because it’d probably take more than a thousand words for me to accurately describe what I saw. Aside from the many problems with the TPR valve, what are your thoughts regarding the location of the pressure regulator. It sits between a valve (possibly the main cutoff) and the water heater. I’ve never seen this configuration. Ever. Are there any requirements regarding the placement of the pressure regulator?
From here, it looks like the pressure regulator is located just past the main water supply entrance valve which is OK.
Yep, “If” that’s the main water supply entrance valve and not the water heater supply valve. I wasn’t able to locate a main supply valve anywhere else in the house, and it was only 1,400 sq ft.
Where’s the rest of the cold water plumbing?
Right in the center you’ll see the valve after it comes out of the wall.
OP suggested that might be the main water valve. Should be house plumbing after the regulator or at least the main valve.
Why was the TPR valve installed on the hot water line? It looks to me like the probe on the TPR valve will not engage hot water unless the water heater is ran. I have my doubts that the hot water running through those pipes will reach the probe of the TPR valve even when the house hot water is running. The house is being supplied with a half inch hot water line. Was there not a place to install the TPR valve properly into the water heater? That’s a very strange configuration for the pressure reducing valve. I would like to see a valve that isolates only the water heater as well. Is that flue pipe screwed to the water heater diffuser? Definitely amateur hour.
I would research the installation manual for this particular brand of water heater. I would refer this installation to a licensed plumbing contractor for correction.