What is the primary function of a trap in plumbing fixtures?

The primary function of a trap in plumbing fixtures is to prevent sewer gases from entering the building. Traps are designed to hold a small amount of water at all times, creating a barrier that blocks harmful gases from the sewer system, such as methane and hydrogen sulfide, from escaping into the living space. This is crucial for maintaining indoor air quality and protecting the health and safety of the building’s occupants.

While traps do assist with drainage by allowing wastewater to flow through while retaining water, the principal purpose focuses primarily on sealing off air and odors, making the prevention of sewer gas intrusion the top priority. Traps also do not actively filter sediment; that function is typically managed by other plumbing devices such as filters or strainers. Additionally, while reducing water usage is an important aspect of plumbing design, traps are not primarily aimed at conserving water; their main role is to maintain a hygienic barrier against harmful gases.