A commercial building project requires the installation of a new 3-inch (75 mm) soil stack using PVC pipe. The local plumbing code specifies that all PVC DWV joints must be solvent-welded. Which of the following is the most critical step to ensure a strong, leak-proof joint when solvent-welding PVC pipe?

Question: A commercial building project requires the installation of a new 3-inch (75 mm) soil stack using PVC pipe. The local plumbing code specifies that all PVC DWV joints must be solvent-welded. Which of the following is the most critical step to ensure a strong, leak-proof joint when solvent-welding PVC pipe?

Answer options: ✅ Applying a continuous, liberal coat of primer, followed immediately by cement, and ensuring full engagement and a quarter-turn upon insertion.

• Heating both the pipe and fitting to 60°C (140°F) before applying solvent cement.
• Using only clear PVC solvent cement, as coloured cement can indicate impurities.
• Allowing the primer to dry for at least 15 minutes before applying the solvent cement.

Correct answer: Applying a continuous, liberal coat of primer, followed immediately by cement, and ensuring full engagement and a quarter-turn upon insertion.

Explanation: For a strong solvent-welded PVC joint, proper application of primer and cement, coupled with full insertion and a quarter-turn to distribute the cement evenly, is critical. Primer softens the surfaces, and immediate cement application ensures proper fusion. Heating the pipe, using only clear cement, or allowing primer to dry for too long are incorrect practices for standard PVC solvent welding.