The once every 6 months is a sales gimmik. It is intended to say "Hey look here! Arn't we doing a lot for the small fee of just $69.99* we charge to service your HVAC unit twice a year? (*freon, travel time over 1.3 miles, servicemans lunch break fee, and other parts not included) ;-)Granted you should service your heating system ibefore winter and your AC before summer every year. That is where they get the every 6 months from.
Heidi, there is no reason to clean the drain lines unless something is clogging them and the condensate overfills the catch pan under the AC units. There are safety switches and alarms (not on all models) that keep the trays from over filling. You will know well ahead of time if the tubes are plugged.
As for where the water is coming from; Refrigeration units cool things by removing moisture from the air. Hence the name air "conditioner". This is true with refrigerators, freezers, air conditioners, and large commercial plants. The only difference is the air that they do this to. A refrigerator or freezer only conditions the air inside of it. A home air conditioner conditions the air inside your home. A commercial plant conditions the whole warehouse.
To remove the moisture in your home the AC fan takes the air inside your home from the return air duct (this is where you install the air filter at) and blows it over the evaporator coils inside the AC unit. As the air passes over the coils the moisture in the air condenses onto the coils. It is just like a kitchen window in the winter when a lot of holiday cooking is going on. It collects moisture because it is colder than the air in th ekitchen. The warm moisture laden air releases the moisture as it cools against the cold window and you get condensation.
The water you see dripping from the pipe is the condensation that is from the moisture that the unit is removing from the home. It is perfectly normal to have a little bit of water come from the AC unit. The "normal" amount should not be more than dripping. If at any time it becomes a steady dribble the unit should be looked at.
Here is a video I made to illustrate the difference.
Please click here to see the video.
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