What is the minimum slope required for underground ducts to allow drainage?

The minimum slope required for underground ducts to allow for proper drainage is 1/8" per foot. This specification ensures that any condensation or moisture within the duct system can effectively flow toward the designated drainage points, preventing water accumulation which could lead to performance issues, corrosion, or mold growth within the ductwork.

A slope of 1/8" per foot provides a balance that is sufficient to facilitate drainage without creating too steep of an incline, which could complicate installation or result in material stress. This slope is commonly accepted in various building codes and standards concerning duct installation, ensuring consistency and reliability in drainage performance throughout different installations.

In contrast, steeper slopes can create unnecessary challenges in installation and maintenance, and flatter slopes may not provide adequate drainage, allowing moisture to sit and potentially cause damage over time.