What minimum pressure variation must be sustained at the 2” fixture trap for a 100% safety factor?

The correct answer is related to the critical concept of maintaining adequate water pressure in plumbing systems to ensure proper drainage and prevent siphoning in traps. For a 2” fixture trap, the minimum pressure variation that must be sustained is specifically set at 1” of water column (W.C.) to incorporate a 100% safety factor.

This parameter is essential because fixture traps prevent sewer gases from entering a building while allowing wastewater to flow freely. If the pressure variation falls below this mark, there's a heightened risk of the trap losing its water seal, which can lead to undesirable backflow and potential health hazards.

In plumbing design, a safety factor is integrated into system calculations to accommodate unforeseen circumstances, such as fluctuations in water pressure due to demand or pressure surges. By setting the minimum requirement at 1” W.C., plumbing engineers ensure that the traps reliably maintain their function even under varied conditions.

Understanding this principle is vital for plumbing system design, as it aids in preventing problems related to drainage and air quality within buildings.