Journeyman Plumber ExamTools, Equipment, and SafetyMedium
When working with PVC pipe and fittings, a plumber uses a specialized primer and cement. What is the primary purpose of applying the primer before the cement?
- ATo lubricate the pipe for easier assembly.
- BTo provide a watertight seal without the need for cement.
- CTo clean the pipe surface and soften it for better solvent welding.
- DTo prevent UV degradation of the pipe material.
Show answer & explanationAnswer & explanation
Correct answer: C. To clean the pipe surface and soften it for better solvent welding.
PVC primer is a crucial component in solvent welding. Its primary purpose is to clean the pipe and fitting surfaces, removing dirt and grease, and more importantly, to soften and dissolve the outer layer of the PVC material. This softening allows the subsequent PVC cement to chemically fuse the pipe and fitting together, creating a strong, monolithic joint.
Why the other options are wrong
- A. Primer's role is not lubrication; it's about preparing the surface for a chemical bond.
- B. Primer is a preparatory step; it does not create a watertight seal on its own, which is the function of the solvent cement.
- D. UV protection for PVC is typically inherent in the material's formulation or applied as a protective coating, not a function of the primer.
PVC Solvent Welding Primer
A chemical solution applied to PVC pipe and fittings before cement, designed to clean and soften the plastic surface for optimal solvent fusion.
- Cleans dirt and grease
- Softens/pre-dissolves the PVC surface
- Enhances bond strength of solvent cement
- Required for most PVC piping codes
Memory trick: Prime to Prep, Cement to Connect.