Vent pipes must be at least how many feet from any vertical surface?

Vent pipes need to be positioned adequately to ensure effective airflow and to prevent any potential obstruction or contamination from adjacent surfaces. The correct requirement is that vent pipes must be located at least 1 foot away from any vertical surface. This distance helps maintain the integrity of the venting system, allowing it to function properly without interference from walls, fences, or other structural elements.

This spacing also reduces the risk of blocking the vent pipe, which could lead to pressure changes and possible backflow of air inside plumbing systems. Adequate separation from vertical surfaces is crucial for preventing potential issues with drainage and ensuring that gases can escape freely from the system.

The other options represent distances that exceed the requirement, which is specifically established to facilitate proper venting without unnecessary restrictions.