Installation Guide

26 Rinnai Tankless Water Heater Installation and Operation Manual
Two types of venting options are available:
Room Air (Indoor)
Room air is used for
combustion while exhaust
vents to the outside.
External (Outdoor)
Concentric Pipe (Indoor)
Intake air and exhaust vent
directly through a single
concentric connection. Hot
exhaust exits through the
interior tube, while intake air
enters through the outer
layer.
Twin Pipe (Indoor)
Intake air and exhaust
vent directly through
separate penetrations.
Water heater with
outdoor vent cap.
Direct Vent
Multiple water heaters sharing an air intake
header and a separate exhaust header that
vents directly through separate penetrations to
the outside
Non-Direct (Room Air) Vent
Multiple water heaters using room air for
combustion while sharing an exhaust header
that vents directly to the outside.