What could cause a trap to lose its seal if it is set more than 2 feet below the fixture outlet?

When a trap is set more than 2 feet below the fixture outlet, the primary concern is the impact of momentum on the flow of waste water. As wastewater exits the fixture, it moves downward due to gravity, gaining momentum. If the trap is too deep, this increased momentum can cause the waste water to push through the trap too forcefully, potentially displacing water already within the trap.

In simple terms, the momentum of the fast-moving wastewater can disrupt the water seal, which is intended to prevent sewer gases from entering the living space. If the water seal is broken, foul odors and harmful gases may rise from the drainage system into the area above.

This phenomenon emphasizes the importance of maintaining an appropriate height for traps to ensure that the seal remains intact and effectively prevents sewage gases from escaping into the home. Understanding this principle helps plumbers design systems that maintain proper trap installation, ensuring both functionality and safety for residential plumbing systems.