AC drain clogs almost daily

[brax71]

Help, what do i do????

I can't figure out what keeps causing it, but my AC drain clogs very frequently.  I've tried vinegar, I've tried bleach, I've tried the condensate drain cleaner from Home Depot, I've tried a shop-vac on the pipe outside.  Nothing seems to last more than a day or two. 

BACKGROUND:
- 5-ton Heat pump installed in March, works like a champ when it's not clogged.
- Second heat pump (2 ton) installed at same time hasn't clogged yet.
- I'm in the Tampa area, so it's SWAMPY. With the recent storm pattern, it has seemed even more humid than usual lately.
- I pulled the side off of the inside unit about two weeks ago, and the drain tray had white slime that kind of looked like wet toilet paper that's disintegrating; i cleaned that out as well as possible an then crawled into the intake underneath the inside unit to clean more of it up, and then sprayed a coil cleaner on the fins, followed by a water rinse.  That lasted a couple days.

I've lived in a number of houses and have never had anything like this before; I'm really stumped.

Thanks,
Andy

[EightFingers]

Might try a descaler like that used in cooling towers.
Maybe rig up an air compressor to blow it out?

[frule]

This fix works perfectly. It also cleans out the p-trap. I use Viper spray on the "A" coil and pan tabs. I think 
that your problem is that you aren't really getting the drain pipe cleaned out well enough.
 https://www.youtube.com/watch?v=Jme-TcYAqZE

[brax71]

thanks for the recommendations.
My A/C closet upstairs is very tight, so there's no room to add a hose hook-up like in the video, so i shoved a garden hose down the pipe.  I ran water while the wife watched the drain pipe outside.  She didn't see anything yucky coming out, and said it was flowing clear and strong.

I also pulled the side off of the unit and there wasn't any more slime in the pan that i could see.  i dumped a bit more bleach in the pan (i know, risk of corrosion -- but i'm going "scorched earth" for now).  lastly, i used a bottle brush-style thing to scrub inside the short pipe between the pan and the float switch.

I'm hopeful that the combination of previous efforts (shop-vac + chemials) and today's water flushing and scrubbing may do something.

[arthropod98]

we actually had a similar issue with our unit maybe 1-2 years ago.  the place that installed it was just doing a routine check on the system, and saw this "film" on the coils.  they asked if i tried to clean it at some point, which i didn't, and they never did figure out WTH the stuff was.  almost seemed like some kinda coating on the coils that was sluffing off after a few years  --  who knows though.  


oh, and it's terrible having the air handler in the attic.  

[blackhat]

Hard to say what’s going on but I would start by looking at all the return ducts and the filter box. If dusty dirty air is getting past the filters and into the air handler, clogs are a gimme.

[Woodenfish]

I would replace the drain line. Your never going to be able to clean it out. Make sure the new one is vented at the top and the drain has a proper horizontal pitch.