How does a drain-waste-vent system ensure trap seals remain functional during flush cycles?

How does a drain-waste-vent system ensure trap seals remain functional during flush cycles?

• A. By providing venting that prevents pressure changes and avoids siphonage on traps.
• B. By increasing the water temperature in traps.
• C. By sealing traps with no-air requirement.
• D. By diverting all wastewater away from traps.

Answer: (A)

Ventilation in a drain-waste-vent system prevents siphonage of trap seals during a flush. When water rushes through the drain, it can create a sudden drop in pressure upstream of the trap. If air can’t enter, that negative pressure can suck water out of the trap, breaking the seal and allowing sewer gases to escape. The vent pathway provides an air route to balance pressure as the water moves, so the trap water stays in place and continues to function as a barrier. So, the system’s venting keeps traps from losing their seal during flush cycles. Increasing water temperature won’t stop siphonage, traps don’t work with “no-air” requirements, and diverting wastewater away from traps defeats the purpose of the trap by removing its gas-blocking function.

Ventilation in a drain-waste-vent system prevents siphonage of trap seals during a flush. When water rushes through the drain, it can create a sudden drop in pressure upstream of the trap. If air can’t enter, that negative pressure can suck water out of the trap, breaking the seal and allowing sewer gases to escape. The vent pathway provides an air route to balance pressure as the water moves, so the trap water stays in place and continues to function as a barrier. So, the system’s venting keeps traps from losing their seal during flush cycles. Increasing water temperature won’t stop siphonage, traps don’t work with “no-air” requirements, and diverting wastewater away from traps defeats the purpose of the trap by removing its gas-blocking function.