Drainage, Waste & VentQuestion 18 of 120
A single 3 in vent stack is 46 ft in developed length and serves a drainage stack. If the code limits a given vent size to a maximum developed length, exceeding that length requires which action?
a.Reducing the vent one pipe size
b.Increasing the vent one pipe size for its entire developed length
c.Installing a trap primer at the base
d.Sloping the vent at 1/4 in per ft
Explanation
When a vent exceeds the maximum developed length permitted for its size, the vent must be increased one nominal pipe size for the entire developed length, not just the portion over the limit. Reducing the size makes the friction loss worse, a trap primer only replenishes trap seals, and vents are graded only enough to drain condensate back to the drain, which does not correct an over-length vent.
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