Which of the following is the correct clearance distance for a plumbing vent above a window or door?

The correct clearance distance for a plumbing vent above a window or door is 3 feet. This requirement is in place primarily for safety and air quality reasons. The vent serves to release sewer gases outside, and maintaining a minimum distance ensures that these gases do not enter living spaces through windows or doors.

By having a standard clearance of 3 feet, local plumbing codes help to protect the home's occupants from potential dangers associated with sewer gas exposure, which can be harmful or even toxic. The guideline also accounts for the fact that when windows or doors are open, especially in adverse weather conditions, any foul odors or gases from the vent will not readily enter the home.

The other distances presented do not align with typical plumbing code requirements for such clearances, as they may be too restrictive or excessive, therefore not standard practice. This standardization allows for uniformity across various buildings and simplifies compliance for home inspectors and builders alike.