According to the IRC, what is the danger of S traps in plumbing systems?

S traps are designed in a way that can lead to a siphoning effect, which is a significant concern in plumbing systems. When water flows through an S trap, it can create a vacuum that might pull the water seal out of the trap. This water seal is crucial as it prevents sewer gases from entering the living space. If the water seal is compromised due to siphoning, these hazardous gases can escape through the plumbing system and potentially enter the interior of a building, posing health risks to occupants.

The issue of siphoning is particularly problematic because it doesn't necessarily arise from visible blockages or obvious plumbing issues; it can occur during normal use when the drain is emptied too quickly or when multiple fixtures are used simultaneously. Thus, maintaining the integrity of the water seal in plumbing systems is essential for both safety and sanitation.

While other factors such as potential blockages, air trapping, and leaks may also be relevant to plumbing design, the specific danger associated with S traps is their ability to siphon sewage gases when the trap's water seal is lost.