Where should a trap be placed in a plumbing system?

A trap is a crucial component in a plumbing system designed to retain a small amount of water to create a seal against sewer gases while allowing wastewater to flow through. The optimal placement of a trap is directly beneath a fixture, such as a sink, toilet, or shower, where it can effectively capture and retain wastewater. This positioning ensures that the trap can function properly, maintaining the necessary seal and preventing odors and gases from entering the living space.

When traps are installed directly below fixtures, they are able to collect the wastewater immediately as it leaves the fixture, thus preventing any backflow of sewer gases. This is essential for maintaining hygiene and air quality within the home. Properly placed traps also help in preventing insects and pests from entering the plumbing system through the drainage pathways.

In contrast, placing traps at other locations, such as the main drain line, septic tank exit, or within a crawl space, would not effectively serve the trap's purpose, potentially compromising the integrity of the plumbing system and allowing sewer gases to emerge into occupied areas.