The 2 types of connections are refered to as steamer and 2 1/2 most places use the steamer, usually 5" connection because of ease of use, amount of flow and less friction loss (resistance) as for the type of hydrant it might be a dry type which means there is a stem from the top of the hydrant down to the H20 main as to prevent freezing. in warmer places the use a hydrant like you see in the movies and this picture when someone runs it over the water shoots out... there is water up to street level.
Hope i covered it
Thanks Denny
