What is the minimum height that a fresh air inlet must extend above grade?

The minimum height that a fresh air inlet must extend above grade is 6 inches. This requirement is in place to prevent contamination of the air supply by ensuring that the inlet is high enough to avoid being compromised by surface water, debris, or other potential pollutants that may be present on the ground. This height helps maintain the quality of the air feeding into the ventilation system, which is essential for the proper operation of plumbing and drainage systems within buildings.

Maintaining an inlet at this height minimizes the risk of backdrafting, where outside air—potentially containing harmful substances—enters the system. Additionally, excess moisture or particulates can be avoided, thereby reducing the likelihood of clogs and ensuring that the system functions efficiently. The specifications for fresh air inlet height are part of plumbing codes designed to protect the health and safety of building occupants, emphasizing the importance of proper ventilation in creating a safe indoor environment.