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A trap arm that does not use siphonic action may change direction in a horizontal plane by up to how many degrees between the fixture and the vent fitting?

  1. 45 degrees

  2. 90 degrees

  3. 135 degrees

  4. 180 degrees

The correct answer is: 135 degrees

A trap arm that does not use siphonic action is typically installed at a slope of 1/4 inch per foot and can change direction in a horizontal plane by up to 135 degrees. This means that the trap arm can have multiple bends and turns, but the combined changes in direction cannot exceed 135 degrees. Options A, B, and D are incorrect because they exceed this limit and may cause issues with the proper functioning and venting of the plumbing system. Option A (45 degrees) is too small of an angle and may cause water and waste to have difficulty flowing through the trap. Option B (90 degrees) may create too sharp of a turn and cause air pockets to form, leading to potential blockages. Option D (180 degrees) would essentially reverse the direction of the trap arm, causing a lack of ventilation and potentially creating an airlock.