Paul Franklin wrote:
On Mon, 17 Aug 2009 10:12:51 -0400, "Stormin Mormon"
wrote:

Once in a while, I have need to clear a clogged drain line
from an AC unit. Now, is one of those times. I've got a
maybe job. We'll know in a couple days if I have the job or
not. Big system, 8 ton unit. The building has a couple 12
ton and five eaches 8 ton AC. The drain line is about an
inch or 1 1/4 inch copper, with a vertical open top tube to
pour in some cleaner, or insert a blow gun tip. The drain
which is clogged is about 10 feet long, with maybe 3 elbows
invovled. Drains onto a rolled black rubber roof, so I'm not
eager to use chemicals.

Compressor and blow gun tip comes to mind. What other
options are there? My parts house has a little thing with a
carbon dioxide cylinder. Wonder if that's big enough.

Back in the good old days, we'd use a tank of freon to blow
it out. That's no longer done, of course.

If you can get a garden hose up there, use a drain king. It's a
rubber device you attach to end of hose and slide into end of pipe.
When you turn on the water, it first expands to seal against the sides
of the pipe, and then releases water pressure into the pipe.

I've used them many times to clear undersink drains. Works like a
charm. Come in different size ranges.


Not really necessary; the algae clog is VERY slight - more like a spider web
in strength. If you can wrap your lips around the pipe, you can blow it
loose (don't suck).