A U-trap in an Air Handling Unit (AHU) is crucial for proper condensate drainage and preventing air leakage. When the AHU operates, condensate forms on the cooling coil and drains through the U-trap. The trap’s water seal prevents air from being sucked into the AHU, which could disrupt system pressure and efficiency. It also blocks unpleasant odors or contaminants from entering the system via the drain. The U-trap must be correctly sized to handle the static pressure of the AHU; otherwise, water may not drain properly, leading to overflow, water damage, or mold growth, affecting system performance and indoor air quality.