I learned this from Dan holohan book Classic hydronics

Slowpoke

I'm always asking for help so thought this might help some one. I'm about 1/3 through the book it says that having the expansion tank before the circulator is the best way to pipe and that the automatic air vent should be on the supply side.

Do you know if it is ok to pipe a expansion tank Horizontally on a vertical pipe? I think so but not sure.