At what minimum height above the flood level rim of the fixture must a vent pipe rise vertically before being offset horizontally?

The vent pipe must rise at least 6 inches vertically above the flood level rim of the fixture before it can be offset horizontally. This requirement is crucial in plumbing to prevent any potential backflow of sewer gases into the living space, ensuring that the system remains properly ventilated.

Rising the vent pipe to this specified height above the flood level rim creates a sufficient air gap that maintains the effectiveness of the venting system. It allows for air to freely enter the drainage system, equalizing pressure and facilitating the normal flow of wastewater. By adhering to this standard, it reduces the risk of water siphoning out of traps in fixtures due to pressure differentials created during drainage events, which can lead to unpleasant odors and potential health hazards.

In summary, maintaining a minimum vertical rise of 6 inches is a critical code requirement in plumbing design to ensure safety and functionality within wastewater systems.