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.

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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.

The pipes you see coming through the wall outside are for the overflow pan for the water heater and the relief valve for the water heater.

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There should be two condensate drain lines.

The main drain line comes straight out of the coil enclosure and down the house waste stack.
The secondary drain is a short pipe coming out of the coil enclosure that will spill into the overflow pan if the main drain line is clogged. The overflow pan will then have a drain line that exits the house to drain water in a conspicuous location. If the homeowner sees water draining from this line in the conspicuous location, they should know that the primary drain line is clogged and the maintenance is needed.
Finally, a float switch should be installed on the overflow pan to shut off the A/C completely if the secondary drain is clogged too.