Oh, Joy of home ownership :(

[space-time]

"Slip the vac nozzle a couple inches up over the external pipe drain,"

is this the drain located in the AC closet inside, or the pipe outside? as I said, I think I know where the drain is outside, but I just looked again and I cannot see the PVC pipe

I was thinking something like liquid plumber or drano (or whatever the competitor of liquid plumber is called). Or just get one of those long snakes and push it down the pipe from inside?

I can also call an AC guy if all else fails, but I would rather learn to deal with this myself for next time it happens