Trade Exam · Module 4
Traps and Interceptors
Master trap design: P-trap vs S-trap prohibition, seal depth and slope requirements, one-trap-per-fixture rule, and commercial interceptor sizing and maintenance.
Key Takeaways
- Trap seal depth: minimum 2 inches, maximum 4 inches of standing water.
- Trap arm slope: 1/4 inch per foot downward toward drain; maximum 45 degrees.
Traps are the silent protectors of plumbing systems. They keep sewer gases and pests out of buildings. I have been installing them for decades—get them wrong and you are looking at a house full of sewer smell and angry customers.
Why This Matters on the Exam
Trap design is fundamental. The C-36 exam tests seal depth, trap arm configuration, one-trap-per-fixture rules, and why S-traps are forbidden. Commercial interceptors round out the questions. Common failures happen from improper slope, missing traps, and undersized interceptors.
Keep reading — unlock the full lesson
You’re reading a free preview. Get the complete lesson plus everything you need to pass the California C-36 exam:
- All 63 in-depth lessons
- 1,200+ practice questions
- AI tutor (100 messages included)
- 18+ hours of audio lessons
- Full-length practice exams
- Pass guarantee
More lessons in Finish Plumbing Installations
- 1Fixture Installation
- 2Water Heaters
- 3Backflow Prevention
- 4Traps and InterceptorsYou are here
- 5Accessibility and Specialty Systems
- 6