If your ac unit is not sealed properly, the warm air finds its way to get inside the unit in no time. When this warm air mingles with the cold air already present inside the unit, it condenses and excess moisture builds up. 1.This excess moisture then leaks from your unit. 2.Cold temperatures During the onset of winters, when outside temperatures drop, the process of evaporation slows down, causing a water build up in the unit. Dirty filters A clogged, dirty air filter restricts the air to reach the evaporator coils. As a result the coils get too cold and freeze, and this creates a big block of ice. 4.Low refrigerant levels Just like a dirty air filter, low refrigerant levels cause the evaporator coils to freeze. When the ice melts, the condensate pan overflows and the water leaks. 5.Disconnected drain lines Improper installation of the air conditioner leads to disconnection of the drain line from the unit, which results in the leakage of water from your air conditioner 6.Clogged drain line Accumulation of dust and dirt in the drain line of your AC unit clogs the drain line.