An open vent pipe that passes through a roof should extend at least _____ inches above the roof.

An open vent pipe that passes through a roof should extend at least 6 inches above the roof to ensure proper ventilation and to prevent any potential blockage or backflow of gases. This height requirement is crucial for maintaining air circulation within the plumbing system, allowing harmful gases to properly disperse into the atmosphere without posing risks to health and safety.

Additionally, a vent pipe that extends above the roof by this minimum height helps to reduce the likelihood of being obstructed by snow, debris, or other environmental factors, thus ensuring that the plumbing system continues to function effectively. Adhering to this standard is part of proper plumbing practices as outlined in relevant building codes and regulations.