Red Seal Plumbing Practice Exam

What is the minimum trap arm length for a floor drain?

1. 12" (300mm)

2. 18" (450mm)

3. 24" (600mm)

4. 30" (750mm)

The correct answer is: 18" (450mm)

The minimum trap arm length for a floor drain is typically 18 inches (450mm). This is because a floor drain is designed to handle larger volumes of water and debris, so it requires a longer trap arm to prevent clogging and blockages. Option A is too short and would likely result in frequent clogs. Options C and D are longer than necessary, which may cause unnecessary installation difficulties and increase costs. Additionally, a longer trap arm could potentially lower the water pressure in the drain and impact its functionality.