Which statement is true about underground duct installation?

• A. It should be encased and sloped to allow drainage
• B. It should be buried without any casing
• C. It should be left uninsulated
• D. It should be larger than needed

Answer: (A)

Underground duct installation must be protected from soil and moisture and positioned so any water can drain away. Encasing the duct provides a sturdy barrier against soil pressure, moisture, and potential backfill damage, while sloping the line lets condensate and groundwater flow away rather than pooling around the duct. Burying without protection subjects the duct to moisture and damage; leaving it uninsulated invites condensation and energy loss; making it larger than needed wastes material and increases cost without benefit. So, encasing and sloping for drainage is the proper practice.