What protects trap seals from leaking sewer gases back into a building?

The correct answer is associated with vents. Vents are an essential part of plumbing systems that help maintain the proper functioning of traps by allowing air to enter the drainage system. This airflow equalizes the pressure in the pipes, ensuring that the water seal in the traps is not siphoned off when fixtures are used or when water flows through the system.

When a plumbing fixture, such as a sink or toilet, is used, water flows through the trap, creating a seal of water that prevents sewer gases from escaping into the building. If there were no vents, changes in pressure within the drainage system could cause this water seal to be disrupted, potentially letting harmful and foul-smelling sewer gases enter living spaces. Therefore, proper venting is crucial in preserving the integrity of the trap seal and ensuring that the plumbing system functions effectively and safely.

In contrast, traps are designed to hold a small amount of water to form this seal, drainage systems facilitate the flow of wastewater, and cleanouts provide access for clearing clogs. While each of these components plays an important role in overall plumbing functionality, it is the vents that specifically prevent the intrusion of sewer gases into buildings by maintaining the necessary air pressure in the drainage system.