What is the purpose of a plumbing trap in drainage systems?

The purpose of a plumbing trap in drainage systems is primarily to prevent sewer gases from entering a building. Traps are designed to hold a small amount of water, creating a seal that blocks the passage of gases from the sewer system into living spaces. This is vital for maintaining indoor air quality and ensuring the health and safety of inhabitants. The standing water in the trap acts as a barrier to odors and harmful gases, effectively protecting the environment inside the building.

In addition to their role in preventing sewer gases, traps also help in collecting debris and preventing clogs in the drainage system. However, their primary and most critical function is indeed to act as a seal against harmful fumes.