• With a multi-floor system, in addition to
the quick vent on the supply main, additional
quick vents should be installed at the
top of every upfeed riser. Without these additional
vents, the higher floor heat emitters
can receive steam later than those on lower
floors. Figure 2.
National Oilheat Research Alliance 11
One Pipe Systems
In a one pipe gravity system both steam and
condensate travel in the supply main. Figure 1
1. One Pipe Parallel upfeed gravity return
system with wet return.
• The supply main on these systems
must maintain a minimum of 1" per 20'
pitch downwards towards the return. The
preferred pitch is 1/4" per ft. Sags in the
main will cause water hammer.
Figure 2