I live in a condo with an in-home AC/heat pump. This morning we noticed that it was dripping water, and when we took off the front panel we could see standing water in the run-off tray. It was pretty clear that there was gunk (probably built-up dust) in the bottom of the tray, so we assume there's a bunch of it clogging the PVC piping too.
What is the best way to clean this out? We have one snake tool, but unfortunately it only reaches to about the top of the U-bend. I read that Drano is not a good idea, because without water pressure from above, it could sit in the U-bend and corrode the pipes. We poured about a cup of vinegar in this morning and are going to let that sit all day to see how it does. Is there anything else we can do if this doesn't work? We don't really want to have to call a plumber if it's just a clog job.
Update: All the vinegar drained through. Filled it again and it's a slow drain, though better than it was before. Hopefully a few runs of this will do the trick.
Here's some pictures to give you a better idea what I'm dealing with. The left shows the PVC piping. The right shows the coils, with the drainage tray underneath. The water pools underneath that lowest coil.