re: A/C drip pan full. Bleach down PVC drain pipe?

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In most cases the A/C drain line is tied into a house drain line. There is normally not a drain line for the secondary pan. The pan has a float switch that cuts the power to the A/C when the pan fills up.

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Mine is tied into the house drain line (actually a vent stack in the attic), I had the secondary pan line run so I don't have to wake up sweating or come home to a 100 degree house when my main line stops up. The float switch is still there too, just in case the secondary pan line is stopped up somehow.

I have seen a lot of older homes where the main line drains outside. I would guess those probably had the units added after the fact and the installers didn't want to mess with the cast iron vent stacks for the main drain.