I have a hot water heater at a rental house that has some sort of secondary pressure valve coming off the supply line from the house and the top of the hot water heater. Is anybody familiar with this set up? It is leaking at a steady pace at the side of the house, I’ve tested the house pressure and it is within specs. I am a rookie DIY’r so not technically familiar with how this interacts with the Hot water heater or the traditional pressure relief valve (which is not leaking). I will post a few pictures I had taken when I did a previous repair, to show the part I am taking about. It has a small coper pipe coming off of it, not sure the exact size approximately 1/4”. If anybody can help me identify this part and if what would cause it to be leaking? Ideas on how to fix it?