VENT EXAMPLES FOR SINGLE FLUE
Max Vent Run - 40 ft. Equivalent With Three (3) 90° Elbows
Special Note: The vent terminal 90° elbow and first 90° elbow off back of the heater, when within 6” (15.2 cm), do not contrib- ute to the overall vent length measurement. For each 45° elbow installed in the horizontal run, the length of the horizontal run MUST be reduced by 1.5 feet (45 cm). This does not apply if the 45° elbows are installed on the vertical part of the vent system. Reduce the length of the horizontal run 3 feet (91.4 cm) for every 90° elbow.
Note: On horizontal runs, a P.V.C. support clamp needs to be installed every 3 feet. No “sags” in horizontal vent runs; water will settle in the pipe.
When installing a single flue horizontal, the minimum vent length protruding from the outside wall is 6” (15.2 cm). See Figure 17.
Minimum vent from the rear of the unit is 12”.
Note: Horizontal discharge 90° elbow must be pointed downward. See Figure 18. All horizontal runs require either a 1/4” per foot rise to run condensation back to the heater, or a 1/4” per foot downward slope to run condensation away from the heater.
Note: All PVC vent run piping can be purchased at a local hardware store. Schedule 40 PVC pipe should be used and cemented.
MIN. 2” 
12” MIN. | H = | 5’ + 2’ = 7’ | ||
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| V = | 27’ |
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| (2) - 90° = | 6’ |
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| Total = | 40’ |
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6” MIN. 12” MIN.
EXTERIOR GRADE
Figure 17
Single Flue - Straight Out Back
Min 6” Outside Wall
Min 2” From Unit to Wall for Intake Air
Min vent length 12”
Figure 18
Single Flue - Horizontal Tall Vent Run
Example Calculation Max Vent Run 40’
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