What is required for the drainage of underground ducts according to code?

For the drainage of underground ducts, it is essential that they slope to an accessible drainage point. This requirement ensures that any condensation or moisture accumulating within the duct system can be effectively removed to prevent moisture-related issues, such as mold growth, corrosion, or reduced efficiency of the ductwork.

Having an accessible drainage point is crucial because maintenance and troubleshooting are simplified when the drainage system can be accessed and serviced. An inaccessible drainage point would hinder the ability to clear blockages or address drainage issues, leading to potential failures in the duct system.

The other answers do not align with the established codes. For instance, a slope to an inaccessible point would not facilitate proper drainage or maintenance. Not requiring drainage at all would neglect the necessary management of moisture that can develop in underground ducts. Lastly, while horizontal alignment can have its place in certain duct configurations, it does not satisfy the critical need for effective drainage, which relies on a downward slope to direct moisture away from the duct system.