Two Pipe Gravity Return Systems
In a two pipe gravity system steam and condensate
travel in separate piping.
1. Two pipe upfeed gravity return system
• The supply main must maintain a
minimum of 1" per 20' pitch downwards
towards the return. Sags in the main will
cause water hammer. The preferred pitch is
1/4" per ft.
• With a multi-floor system, in addition to
the quick vent on the supply main, addtional
quick vents should be installed at the
top of every upfeed riser. Without these
additional vents, the higher floor hear emitters
can receive steam later than those on
lower floors.
• Each heat emitter condensate return must
terminate in the wet return, below the
boiler’s water line.
National Oilheat Research Alliance 19