Return Piping Practice Question

Long Beach Ed

Long wondered about this one and have several theories, but hoping someone can tell me for sure. 



Why did fitters drop vertical returns at the end of a main in the full size of the main's piping until below the water line?  



Inquiring minds want to know. 

Charlie from wmass

Steam and condensate mix

takes up more room than condensate. Many did not do it that way though. I often see the drop to be the small size right from the bottom of the main. The way you have I would prefer.