Problem with baseboard heating

[usa_dreamer2002]

Hi all. I hope someone may be able to help.
I have an issue in my basement. My heating system is forced air for the house and hydronic baseboard for the basement. in a renovation. I decided to add two bedrooms and added two additional baseboard (one for each room). I thought it would be as easy as going to the last baseboard and replace the two elbows that served to create the return line and add the two baseboards. now I turned the system on and no hot water flows through the baseboard. I flushed the system numerous times. so not sure if I reversed the pipes I added. Is there a way to identify which line is the one coming from the boiler (the one that needs to go through the baseboard) without having to trace the pipes throughout the house? all the plumbing is behind walls and it would be really hard to trace the heating pipes from the garage where the boiler is located to the basement.

thank in advance,
Manny

 

[arctic bill]

one could start up the heating and see which pipe is hotter. also by looking at valves and purgers one could tell. There is also the question of balance , you would not want to add several heaters to one heating loop, this would cause that loop to be under supplied with enough water .