CA Plumbing PrepC-36 License Exam Prep
Sign InGet Started

Trade Exam · Module 5

Remodel and Retrofit Work

Lesson 6 of 10~20 minFree previewCurrent as of September 2026Leer en español

Remodels mix old plumbing with new. This lesson covers what the 2025 California Plumbing Code lets you leave alone and what new work must meet, how to connect old materials to new ones, how to avoid overloading an old system, and what to do when you open a wall and find asbestos, lead paint or damage nobody priced in, including the California change order rule and the Cal/OSHA and EPA rules that apply.

Key Takeaways

  • New work in a remodel must meet the code for new work, but you do not have to bring the untouched existing system up to current code (CPC 102.4).
  • A lawfully existing system can stay in use and be repaired in its original design and location if it creates no hazard (CPC 102.2).
  • The alteration may not make the existing system unsafe, insanitary or overloaded, so check drainage and supply loads when you add fixtures.
  • New water piping must be a material in Table 604.1; copper tube is at least Type L (CPC 604.3), and used pipe from other services is not allowed (CPC 604.8).
  • Where metal building supply piping serves as an electrical ground, replacement piping must be of like material (CPC 604.10).
  • Old to new connections use the transition fittings the code lists (CPC 605.16, 705.10), with dissimilar metal joints in exposed or accessible locations (CPC 310.6).
  • Extra work on a home improvement contract needs a written change order, signed before the work starts, that states scope, price change and schedule effect (B&P 7159, 7159.6).
  • Stop and identify suspect asbestos or lead before you disturb it: Cal/OSHA 8 CCR 1529 and 1532.1 apply to repair and renovation, and the EPA RRP rule covers plumbers disturbing paint in pre-1978 housing.

Why This Matters

"Retrofit plumbing" and "repair plumbing" are listed under the Service, Repair, and Remodel section of the CSLB C-36 exam, and "environmental safety" is listed under Safety. On the job, remodels are where scope creep, surprise conditions and hazardous materials meet, so knowing the rules protects both you and the customer.

What the Code Lets You Leave Alone

The 2025 California Plumbing Code (CPC) handles existing buildings in Chapter 1, Division II. These sections are adopted by the local jurisdiction and can be amended locally, so always confirm with the building department.

  • Existing installations (CPC 102.2). Plumbing lawfully in place when the code was adopted may keep being used, maintained and repaired in its original design and location, as long as no hazard to life, health or property has been created.
  • Additions, alterations, renovations or repairs (CPC 102.4). New work must conform to what is required for a new system, without requiring the existing plumbing system to be brought up to the current code. The new work must not cause the existing system to become unsafe, insanitary or overloaded. Deviations from new-construction rules are allowed only where necessary and first approved by the Authority Having Jurisdiction.
  • Existing building sewers and drains (CPC 102.4.1). They may be reused for new work where examination and test show they meet the requirements for new work.
  • Unused openings (CPC 102.4.2). Openings into the drainage or vent system that are not connected to fixtures or vent terminals must be permanently plugged or capped in an approved manner.
  • Change of occupancy (CPC 102.6). If the building's use or occupancy changes, the plumbing must meet the code for the new use.

A common myth is that touching any part of an old system forces the whole system to current code. CPC 102.4 says the opposite: the new work meets current code, and the existing system is not required to be brought up to it, as long as your work does not make it unsafe, insanitary or overloaded.

Would you pass the C-36 today?

Take the free 21-question practice test. About 10 minutes, no account needed. You get your score by section and see exactly where you are losing points.

Take the free test

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 in-depth lessons, exam prep and After the License
  • 1,000+ practice questions
  • AI tutor (100 messages included)
  • 14+ hours of audio lessons
  • Full-length practice exams
  • Pass guarantee
Start Free — Create Account$149 one-time · lifetime access · no subscription

Already have an account? Sign in

More lessons in Service, Repair, and Remodel

Browse all modules
Get Help