Your home's air conditioner doubles as a dehumidifier. It pulls excess moisture from the air, which is then routed through the system and out of the condensate drain. When everything is working properly, this excess moisture should drain away outdoors and pose no issues. If you find water indoors, such as damp carpet or wet wallboards near the location of the external unit, then you may have a problem. Standing water around your external AC unit is also a sign of problems.
The most common reason for water leaks around your air conditioner is a blocked condensate drain line. The consistently damp conditions inside a drain line, particularly when the weather is warm and humid, create ideal conditions for algae and mold growth inside the line or the drain. Growth in the line causes water to backflow and leak around the AC and sometimes into the house. If the drain is blocked, then the drip pan may overflow and lead to leaks outdoors near the AC unit. Regularly flushing the line and drain with bleach will kill the growth and clear out the line and drain so the water flows away as it should.
The evaporator coils on an overworked or dirty system can freeze up, and then water will collect around the unit when the coils eventually thaw. A common reason for freezing is dirty filters or coils. Changing your filters regularly and having the system cleaned and tuned up annually solves this problem. A unit can also freeze up if it is undersized for your home or if there is a leak in the refrigerant lines. It's a good idea to have a maintenance tech out to find the cause if your unit keeps freezing over.
Drain System Leaks
Sometimes the problem is a leak in the drain system. Everything is working properly, but the water isn't draining where it should do to the leak. In this case, you will need to have your drain lines checked for cracks or pinprick holes. A crack in the drain pan can also lead to a leak in an otherwise properly functioning system. Fortunately, replacing a leaking line or a cracked drain pan is a relatively quick and inexpensive repair. Another area where leaks can occur is in the condensate pump, which is responsible for moving the water into the drainage system. If this is the case, then the pump must be repaired or replaced.
Contact an AC maintenance service in your area for more help.