Plumbing connection question

[clowman]

I have a 69 Overlander that I am going to try to correct some plumbing issues. I have a question about the connector to the water heater. If you notice in the picture the brass fitting that connects into the water heater, I have no idea on what size fitting that is. I am planning on using 1/2 PEX and some Flair-it connectors ( thanks for the pictures Roy ).

My question is this... Does anyone know what connector size that brass fitting is?

My dilema is that my camper is 5 hours away, so I can't just go and "check it out" I have to take (hopefully) all I'll need with me.

Thanks for any help. I did take lots of pictures when I went down to check out what I would need, but neglected to get this important detail.

[markdoane]

It's probably 3/8", but why not buy a 3/8" and a 1/2" and return the wrong one?