For a 1 1/4 inch pipe, the maximum distance from fixture trap to vent is?

• A. 3 Feet 6 Inches
• B. 2 Feet 6 Inches
• C. 4 Feet
• D. 5 Feet

Answer: (B)

The key idea is how far a trap can be vented, which depends on the size of the trap arm. The trap arm must reach a vent within a maximum distance to prevent the trap from being siphoned when other fixtures discharge. For a 1 1/4 inch trap, the maximum allowable trap arm length is 2 feet 6 inches. So the vent must be located within 2'6" of the trap. Distances longer than that would risk siphoning the water seal, so they aren’t allowed. The other answer choices exceed this limit, which is why the correct maximum distance is 2'6".