Rheem 627 series Owner's Manual And Installation Instructions page 64

FLUEING
HORIZONTAL FLUE RUNS
There are a number of basic installation requirements which must be followed for a flue installation
incorporating horizontal flue runs.
Failure to observe these precautions can lead to the premature failure of the flue system and / or
water heater.
The flue must be installed with the seam of the inner flue
toward the top of the installation.
A horizontal section of flue must be installed with a
gradient of 20 mm per metre (1 in 50 or 1° fall) of
horizontal run.
A horizontal run of flue between two bends, where the
bend closest to the flue terminal is orientated upward,
must have a gradient upward to the flue terminal.

Condensate will drain back toward the water heater. A Condensate Trap and drain line must be
installed where the horizontal flue is installed with an upward gradient. Refer to
Condensate"
on page 62.
This ensures any condensate formed during operation of the water heater is prevented from
draining back into the water heater.
A horizontal run of flue connecting directly to a Horizontal Flue Terminal must have a gradient downward
to the flue terminal.
This prevents rainwater from entering the flue draining back into the water heater.

Use Male to Male and Female to Female Adapters to reverse the direction of flue insertion where
three or more sections of flue are used in a horizontal flue run and the flue drains toward the flue
terminal. Refer to the diagram
page 64.
This provides for proper draining of condensate without pooling at the flue component joins.
"Typical Installation – Horizontal Terminal with One Bend"
Typical Installation – Horizontal Terminal with One Bend
64
"Draining the
on