What is the primary purpose of maintaining a continuous downward slope in duct piping?

Maintaining a continuous downward slope in duct piping is primarily intended to allow for the drainage of condensation or rainwater. This design feature is crucial because during the operation of HVAC systems, moisture can condense within the ducts. If the ducts are not properly sloped, this moisture can accumulate, leading to potential issues like water damage, mold growth, and reduced indoor air quality.

By ensuring that the ductwork is sloped downward, any condensation that forms can effectively drain away to designated areas where it can be properly managed, preventing buildup and maintaining a safer, healthier environment. This practice also helps in preserving the integrity of the duct system over time by reducing the likelihood of corrosion and microbial growth that could arise from stagnant water.