Trade Exam · Module 3
Water Supply Rough-In
Master water supply materials, pressure control with PRV, hot/cold fixture orientation, support spacing, backflow prevention, and pressure testing before startup.
Key Takeaways
- Minimum residual pressure at highest fixture: 15 psi (CPC 608.1); maximum incoming without PRV: 80 psi.
- Pressure Reducing Valve (PRV) mandatory when city supply exceeds 80 psi; install at service entry; reduces to 60-75 psi downstream.
- Hot water LEFT, cold water RIGHT when facing fixture; universal code rule tested on exam.
Let me show you how water supply rough-in really works on the job. I have been doing this for 25 years in LA and the Bay Area, and I'm gonna tell you straight: get this wrong and you're eating the cost of a callback.
Why This Matters on the Exam
Water supply rough-in is about 12-15% of the test. You've gotta understand materials, pressure control, system layouts, backflow prevention, support, and testing. These are not just academic—they're the difference between a tight system and a nightmare job.
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