Wall-mounted air conditioners drip water primarily due to condensation accumulation and improper drainage. Common causes include dirty evaporator coils, clogged drain lines, or incorrect unit sizing.

The condensation process occurs when warm, moist air passes over the cold indoor evaporator coil, causing moisture to collect as liquid. If the coil is dirty, airflow is restricted, reducing efficiency and increasing condensation. According to the Environmental Protection Agency (EPA), 20–30% of residential AC leaks stem from clogged or improperly installed drain lines. A 2021 study by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) found that 40% of wall-mounted units in homes experience drainage issues due to blocked drain ports or missing slope in the drain pipe. Additionally, undersized units or rooms with high humidity levels exacerbate the problem, as they cannot remove sufficient moisture. The EPA recommends annual coil cleaning and drain line inspections to prevent leaks. For example, a 2019 Energy Star report noted that 60% of AC-related water damage in U.S. homes could be avoided through proper maintenance. Incorrect installation, such as improper mounting or misaligned drain connections, also contributes to 15–20% of leaks, as stated by HVAC industry surveys. Addressing these factors—regular cleaning, drain line maintenance, and professional installation—can reduce dripping by up to 70%, according to ASHRAE data.