Rinnai RU80i Installation And Operation Manual page 40

Piping Diagram for Basic Installation
Water Gas
drain plug connection
Condensate
Hot water
trap drain plug
outlet
The condensate drain pipe (along its entire
length) must be at least the same diameter
as the drain line, (1/2 inch NPT).
40
Cold water
inlet
Condensate
drain line
Refer to the Condensate
section in the venting
instructions
KB Series Manual