During a recent bathroom addition, I installed a new section of baseboard heat. When I purged the system and bled the air through the bleeder valve I wasn't getting the heat to circulate. I decided to install a purge set up on the loop for the new bathroom (this is a monoflow system or aome call a venturi system. When I Cut out the old return side (black iron pipe) it was packed solid with debris, sludge and rust. I also noticed off the main supply and return the are not producing much heat. I can not get water through the new purge set up because of the blocked pipes. What is recommended here? New heating system piping? That is what I think. Any suggestions? Thanks.