Vent Lengths
Intake/Exhaust
Maximum Equivalent Length
SL10-85 G3 SL14-115 G3 SL20-160 G3 SL30-199 G3
(IBCpart P-257)
3-inch PPs
flexible pipe
Limited to 45 ft
maximum
Limited to 45 ft
maximum
Limited to 45 ft
maximum
Limited to 30 ft
maximum
Allow 1.2 x actual
length (e.g., 10
feet of 3-inch
flexible pipe x 1.2
= 12 feet of rigid
pipe)
Allow 1.2 x actual
length (e.g., 10
feet of 3-inch
flexible pipe x 1.2
= 12 feet of rigid
pipe)
Allow 1.2 x actual
length (e.g., 10
feet of 3-inch
flexible pipe x 2 =
20 feet of rigid
pipe)
Allow 3.3 x actual
length (e.g., 10
feet of 3-inch
flexible pipe x 3.3
= 33 feet of rigid
pipe)
Table 4 Maximum air intake pipe and maximum exhaust vent length
Notes
Unused intake travel cannot be added to the exhaust. Unequal intake and exhaust
piping is allowed.
Support should be provided for intake and vent piping, particularly for horizontal
runs (follow local code).
Example of equivalent length calculations for an SL 14-115 G3:
An SL 14-115 G3 can be sited up to 240 feet (actual vent length allowance)from the
vent termination using 3-inch pipe.
For 6 x 90º elbows, the maximum lineal (straight) length of pipe allowed is 192 feet
(240’ – (6 x 8' = 48) = 192').
For 3-inch flexible PPS pipe, up to 45 linear feet is allowed in vertical orientation (> 45
°). The equivalent length of 3-inch flexible PPS pipe should be calculated using a
multiple of 1.2 (e.g., 10' x 1.2 = 12').
3.7.5 Rooftop vent termination
Warning
Condensate can cause corrosion of metal roofing components and other roofing
materials. Check with the builder or roofing contractor to ensure that materials are
resistant to acidic condensate. pH levels can be as low as 3.0.
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