Upon arrival, system was in cooling mode but set high enough that it would not attempt to run. Little spot of water in the attic upon first inspection. Could not find anything around the perimeter of the indoor coil that looked like water spots. Turned on AC to test run operation and see if any leaks were visible. Inspection around attic portion showed no external leaks. Inspected drain line termination at outside near condenser unit and there was no condensation dripping. Suspected drain line to be clogged. Used gallow gun to blow through drain line. Slight pressure build up at first, followed by an audible popping noise, and then water started to flow out of the drain. Initial water was chunky and murky, and gradually got cleaner. Inspected attic portion again and found no leaks. System is properly draining and ready for operation.