Use automatic hot water air vent or regular air vent

heatingFun

I am installing CI baseboard for my hot water heating system. There are two types of air vent:
Automatic hot water air vent, like this one and
Regular air vent, like this one.

Which one I should use?

In the case of automatic hot water air vent, I can shut it off completely during air pressure testing? then how to put it back in the automatic mode, half turn, one turn or one and a half turn?

icesailor

Use the cheap basic one. The auto ones will vent and suck air no matter how hard you tighten them. They all get white and scuzzy.

If you maintain proper pressure in the system, you should never need to vent them unless you drain the system.

If replacing, you should get a proper 1/8" NPT pipe tap. Make sure that it is a correct and proper NPT pipe thread tap. There is a British straight pipe thread tap with no taper and a one thread difference in threads per inch. It won't ruin the threads but it doesn't help them any.

British Standard Pipe Thread (BSPT) will be 1/8"-28 TPI

US National Pipe Thread (NPT) will be 1/8"-27 TPI.

heatingFun

I am glade I asked here. I was planning to use that auto air vent because it is easier to operate.

The #9 CI baseboard has the worst end cover. I have to vent at the end because I cannot remove the screw from the top air vent opening. With that bad end cover, it is really hard to operate the air vent inside the cover.