Drainage, Waste & VentQuestion 29 of 120
A 1-1/4 in trap arm serves a small lavatory. The vent is located 3 ft of developed length from the trap weir. What is the correct evaluation?
a.Acceptable, because any trap arm may run 5 ft
b.Acceptable, because 1-1/4 in arms are exempt from the length table
c.Not acceptable, because a 1-1/4 in trap arm is limited to 2-1/2 ft
d.Not acceptable, because a 1-1/4 in trap arm is limited to 2 ft
Explanation
The maximum developed length for a 1-1/4 in trap arm is 2-1/2 ft, so a 3 ft run exceeds the limit and the arm would need to be increased in size or the vent moved closer. The 5 ft figure belongs to a 2 in arm, no size is exempt from the table, and the 2 ft value understates the actual 2-1/2 ft limit.
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