The one pipe steam circuit system is also called parallel flow system. This is the standard way that one pipe steam is generally installed in the houses we see in the heights areas. The only major difference here from the counterflow system is that the main steam pipe rises to the basement ceiling then gradually pitches downward toward an eventual drop back to a wet return which again feeds the water back to the boiler. The runouts to the radiators and the radiators themselves still drain back into this main steam pipe. But the system operates considerably better than its counterflow cousin since the steam and the condensate travel in the steam main in the same direction. This helps from having the steam squashed by the returning condensate.