What is the required continuous downward slope for above ground duct piping toward the suction point?

The correct answer, which indicates a required continuous downward slope of 1/8 inch per foot for above-ground duct piping toward the suction point, is based on ensuring effective drainage and preventing the accumulation of water or condensation within the ductwork. A slope that is too steep or too shallow can lead to issues such as poor drainage performance, increased risk of blockages, and reduced efficiency in the system.

Maintaining a 1/8 inch per foot slope ensures that any moisture present can drain effectively toward the suction point without causing unnecessary stress on the materials or creating pockets of water that could foster growth of mold or other contaminants. It strikes a balance that supports both practical installation and long-term functionality in residential or commercial settings.

In contrast, a slope that is too steep—like 1/4 inch per foot or 1/2 inch per foot—could potentially strain the piping and create pressure imbalances in the system. Similarly, a slope that is too gentle—such as 1/16 inch per foot—may not provide adequate drainage, leading to the same issues of moisture accumulation and potential system inefficiencies. Therefore, 1/8 inch per foot is the optimal choice for ensuring proper function and reliability of above-ground duct piping