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AC Condensation Overflow

Posted by jjfrisco (My Page) on
Sat, Jun 2, 07 at 23:37

I'm just an average homeowner who usually hangs out in the garden forums. We moved into our new house 3 weeks ago, but the house is 6 years old. The house, including A/C system checked out okay with the home inspector prior to our closing.

This morning when cutting the grass, I noticed water dripping from the attic overhang. I was pretty sure that this was not a good thing.

I went into the attic and checked both AC units. Both are Central A/C units, with a metal drip pan underneath the units. There are condensation lines running out of both units, I assume into a bathroom drain somewhere, but I have yet to find where they terminate. There is also pvc line running from the drip pans, to I believe the attic overhang.

The upstairs unit drip pan had a cup or so of rusty water in the bottom of it. I was pretty sure that this meant the main condensation line was clogged and needed bleach to clear it up. I added an ounce or so of pure bleach to the pvc opening of the main condensation lines for both units. I also noticed that the upstairs unit had some rusty stains inside of the condensation line, but no standing water or algae that I could see.

After adding the bleach, I monitored the rest of the day and still had water coming from the attic overhang when the unit was running. A few minutes ago, I went ahead and added about 1/2 gallon of bleach to the upstairs condensation line. I watched for a few minutes and there is still water dripping from the overflow pvc out of the unit and into the drip pan, then out of the drip pan and into the pvc pipe leading from the drip pan (and presumably dripping out of the attic overhang).

Do I just need to be patient, or is there something else I should be doing. Sorry for the long post, but I'm assuming the more info the better.

Thanks in advance.

Follow-Up Postings:

RE: AC Condensation Overflow

Don't use bleach on a clogged line. It won't clear it and will just cause corrosion on what ever metal it come in contact with and can also accelerate corrosion of the coil in some cases.
You really need to get a hvac company out to check the drains and clear the lines. Rust in the auxillary pan means this has happened perhaps a few times before.
A properly install main drain will have a tee in it before (capped) and after a trap (capped or uncapped) where you can see if and where the drain may be clogged and perhaps use air pressure to see if that will push the obstruction thru.
Other causes could be a system that is icing up, a cracked drain connection, a rusted pan and some systems (carrier) have a metal drip catch on the horizonal units to guide the condensate to the main pan that when dirty runs the water over the coil into the duct.
It's probably just a clogged drain, but as you can see there may be more to it that may need attention.
*I've had to replace many an indoor coil because it rusted out prematurely due to chlorox used the wrong way.

RE: AC Condensation Overflow

Thanks. I tried to use air pressure (high tech method of cupped hand and mouth) and did not notice any resistance. That plus the fact that the 1/2 gallon of bleach drained easily, leads me to believe that the clog is upstream. It would have to be in the few inches of pvc between the A/C unti and the "T" that allows access to the line.

I probably need to make the dreaded phone call to my home warranty company. Any other advice before I do so?

RE: AC Condensation Overflow

jjfrisco. If you have any type of warranty on the house now is the time to call it in.

The AC might or might not be an easy fix. What I notice is you didn't say there is a drain line that would cause water to leak from the attic.

How wet and moldy is the insulation and where else is the water going? Water takes the path of least resistence. If you see it coming out of your attic while cutting grass, and if there isn't a drain tube someone made a path.

RE: AC Condensation Overflow

Only three things come to mind. The primary drain is stopped up. Or, the unit has become tilted such that the secondary condensate drain opening is now lower than the primary. The condensate pan water would flow from the secondary drain into the auxiliary pan. Or, the unit is tilted away from the drain opening(s) to such a degree that the condensate is flowing from the primary drain pan into the auxiliary pan. The auxiliary pan drain piping is supposed to be terminate at a conspicuous location.

We do not normally install a tee in a condensate line. If you blow into the top of the tee, the air pressure will most likely go in the opposite direction of the clogged. What you can do is remove the equipment door to have access to the coil. Plug the opening end of the primary drain and try blowing into the tee again. I am not sure if you can generate enough pressure to clear the clogged line.


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