3. One Pipe parallel downfeed gravity return system
• A downfeed system features an “express riser” that
brings steam to a supply main at the top of the building.
• Both steam and condensate flow downhill in the main
and in the risers.
• Quick vents should be installed near the end of the supply
National Oilheat Research Alliance 15
main and near the end of each down
feed riser.