My Dux Proflo gas hot water system (with water tank) is leaking water. Water is pooling at the base of the hot water tank. Secondly, there is a constant water flow noise coming from near the top of the unit. I know it's water flow because shutting off the water mains stops the water flow noise. I have turned every valve and knob near the hot water unit to try and get the water flow noise to stop, but nothing works except for shutting off the water mains to my house. It's an intense sounding flow - there's a lot moving water, though I can't see it, I can only hear it. I have a plumber coming out in the next day or two.
I am trying to better understand my hot water unit before the plumber arrives, and in particular, what could be causing the water flow noise. Again, the only way it seems I can shut off the water flow noise is shut off the water mains - none of the valves/knobs near the actual hot water unit seems to stop it.
I have attached an image of my hot water unit, marking every input, output and valve. I am looking for a knowledgeable person to please confirm my markings, and to also confirm the purpose of the mystery knobs (3 and 4) and the mystery pipe (6).
Thanks in advance.