Your air conditioner uses an evaporator coil that reduces the temperature (cools it) of the hot air. The process forms the moisture on the coil which is then pushed outside through a drain line. However, if your AC is leaking water into your house, here are a few things that can cause leakage. - Condensate drain line is blocked with sludge, dirt, or dust. - Your drain pan got damaged. - Condensate pump which throws the water outside is damaged. - Air filter is filled with dirt which may block the airflow. - Similarly, low refrigerant can cause the moisture to freeze over the evaporator coil and block the airflow.