What protects the trap from losing its seal when water passes through it?

Proper venting is crucial for maintaining the seal of a trap in plumbing systems. When a trap is installed, it is designed to hold a certain amount of water, forming a barrier that prevents sewer gases from entering the living space. Venting allows air to flow into the plumbing system, ensuring that the pressure is balanced. This balance is essential, as it prevents siphoning or backflow that can occur when water flows through the trap. If the trap is not vented correctly, the negative pressure created by draining water could cause the water seal to be drawn out, compromising its function. Therefore, proper venting is key to ensuring that the trap retains its water seal during and after water passage, thereby protecting the plumbing system from undesirable odors and pathogens.