Strange TPR Valve?

Hello encountered a 2 water heaters in a 1974 built home. One had what appeared to be a TPR Valve but one I have never seen before. Anyone seem these before?

Looks like a pressure relief valve (pressure only) and may be adjustable, can’t read the top of that knob.


Guessing both WH’s are due for replacement anyway…

Looks like a pressure release valve for a water well pressure tank. Not a TPR valve.Write it up hard.


Curious what happened here?

Looks like PVC pipe at the left and top of the picture… with the telltale purple glue. Just more evidence of incorrect/homeowner work.