What is the function of a P-trap in plumbing?

• A. To trap sewer gases and maintain a water seal to prevent odors
• B. To filter solids from wastewater
• C. To regulate hot water temperature
• D. To vent air from the pipes

Answer: (A)

The P-trap works by creating a water-filled bend that blocks sewer gases from coming back into the building. When water drains, a small amount remains in the curved section, forming a barrier (a water seal) that prevents odors and dangerous gases from passing up the drain. It’s this seal that keeps bathrooms and kitchens smelling fresh. The trap isn’t meant to filter solids, regulate hot water, or vent air—the latter is handled by vent pipes, not the trap.