Where should drains be provided in horizontal duct runs?

Where should drains be provided in horizontal duct runs?

• A. At high points in horizontal ducts
• B. At low points in horizontal ducts
• C. At every joint
• D. At the end of the run

Answer: (B)

In horizontal duct runs, moisture tends to condense on the cooled surfaces and then flow downward under gravity. Placing drains at the lowest points allows that condensate to collect and exit the system efficiently, preventing pooling, corrosion, mold growth, and flow obstructions. Draining from high points wouldn’t work because gravity would prevent the condensate from reaching the drain, so water would remain in the duct and cause problems. Draining at every joint or only at the end of the run isn’t as reliable or necessary when a low point drain with proper slope captures condensate along the length of the run. Placing drains at the low points, with the duct gently sloped toward them, provides consistent, effective drainage.

In horizontal duct runs, moisture tends to condense on the cooled surfaces and then flow downward under gravity. Placing drains at the lowest points allows that condensate to collect and exit the system efficiently, preventing pooling, corrosion, mold growth, and flow obstructions. Draining from high points wouldn’t work because gravity would prevent the condensate from reaching the drain, so water would remain in the duct and cause problems. Draining at every joint or only at the end of the run isn’t as reliable or necessary when a low point drain with proper slope captures condensate along the length of the run. Placing drains at the low points, with the duct gently sloped toward them, provides consistent, effective drainage.