Here is a pic of a hot water tank - ( forget the junk on top - the only plumbing is the red pipes - the rest is private owner junk)
I am acustomed to seeing a pressure relief valve and a down pipe from the pressure relief valve to the drain pan. Is it perhaps that red vertical extender with black knob?
I don’t see a TPR valve, but the picture is not great - they are usually installed on the side of the tank.
That black thing you are looking at is a vacuum relief valve.
Water Service Vacuum Relief Valves are used in water heater/tank applications to automatically allow air to enter into the piping system to prevent vacuum conditions that could siphon the water from the system and damage water heater/tank equipment.
I dont see a drain pipe or valve on the tank, but it could be on the back side. If it is, the termination point should be visible, but not like the one below, which terminates into the condenser unit slab.
Thanks everyone - WOW!
So this could be serious - the sale did not go through for other reasons - guess I should inform the sellers realtor of the potentially explosive situation. (I know they are going to say I am alarmist- “…but tank is already three years old and works like magic…”
I’m not convinced the black knob item above the tank is a vacuum relief. Why would you want to enter air into the tank? Never seen any reference to a vacuum break on any water heater information I’ve read. Did you get a close look at the black knob thing?
It consists of a brass body construction with NPT male inlet connection, and a protective cap. Series N36 has a low profile design, is tested and rated to ANSI Z21.22, and is CSA certified. It is suitable for low pressure steam and water service, and is ideal for use in domestic water heaters and supply tanks, table top heaters, jacketed steam kettles, unit heaters, low pressure steam systems, and steam coil heaters. Maximum Working Pressure: 200psi (14 bar), Maximum Steam Pressure: 15psi (103.4 kPa).
I have seen them totally missing. I did a foreclosed property recently that had a 50 gallon electric covered in insulation. I felt all around the tank and could not find one on the side or the top. I just called it out and moved on.