All air conditioners will leak some water but homeowners should know when the leak surpasses a normal amount and needs attention. Leaks can occur from the outdoor condenser unit or from the indoor unit. The thermostat setting and the outside temperature can affect how much condensation your air conditioner produces with normal operation. Higher temperatures and humidity will cause the unit to work harder and produce more water. In general, you should not see more than a small puddle beneath the condensing unit. If the leak is greater than that, or lasts for more than 24 hours, have the system inspected by a professional contractor.
Here is a breakdown of common causes of air conditioner leaks.
Clogged or cracked condensate drain
The condensate drain can occasionally become clogged due to dirt, rust, algae, mold or other debris that builds up over time. Some systems that drain to the outside use gravity to keep the condensate flowing freely, but clogs can cause water to back up and overflow.
Disconnected drain line
An improper air conditioner installation can result in the drain line coming loose, causing the pipe to disconnect. The broken connection means the condensate is not draining into the pan as it should and creates a visible leak.
Cracked or missing drain pan
The condensate pan can rust and crack, causing water to leak from the air conditioner.
Dirty air filter
The air filter keeps dirt and debris out of the air conditioner so that air circulates freely. When the filter gets dirty, airflow over the evaporator coils is restricted. This can cause the coils to get too cold and actually freeze over. Once the coils warm up again and melt, the excess moisture can drip and overflow the condensate pan.
Low refrigerant levels
The evaporator coils can also freeze over as a result of a drop in the refrigerant level. Too little refrigerant causes the pressure in the air conditioner system to become too low. This is another cause of frozen evaporator coils that can lead to a leak.
How to prevent air conditioner leaks
The best way to prevent leaks is with annual professional maintenance. This will keep the lines clear and prevent the condensate drain and pan from becoming excessively dirty during the cooling season.