What if the overflow pipe for your ac unit is overflowing?

First, make sure that it is the overflow. AC units have a condensation line. This is a necessary option as cooling the air causes condensation, much like a cold glass of water will condensate on the outside of the glass. The condensate line should be draining to a safe place, and draining whenever the unit is running. The unit should also have a secondary condensate line (overflow). this line should be separate from the main condensate line and be draining to a conspicuous place. If this line is draining, then you should check to see if the primary drain line is plugged. Anything from lint and dust to dead rats and mice have been pulled out of condensate drain lines. If you do not know how to get to this, call a professional and use the primary and secondary condensate verbiage to let him know that you are not an ignorant putz that he can take advantage of. That should save you a few dollars on the bill. Hope this helps. Terry