AC condensation drain blocked, water overflowing

[scotttx]

I'm in a 40 year old two story home with an attic above, the AC unit is in the attic. The condensation drain empties into a larger pipe which is blocked somewhere, and water is now overflowing from that larger pipe down a wall on the second floor and pooling and dripping through the living room ceiling on the first floor. This is the second time this summer it happened, a few months ago I poured baking soda and 6% cleaning vinegar into it and it worked pretty well, within minutes I heard something flush out down below and the pipe was draining again for awhile. Now it's already blocked again and water is again coming through the living room ceiling. Also, this time the vinegar and baking soda isn't working too well, I've done a few applications, but it is still blocked. At least it can still drain slow enough where if I turn the AC off for a while the water level will eventually go back down.

I've also tried using hot/warm water (can't carry boiling water into the attic, this isn't the easiest location to get to), and hydrogen peroxide. Using a wet dry vac isn't an option here, I can't get a good seal on the pipe since I can't completely lift and remove the the smaller pipe out, due to it being wedged up against the side of a large duct. I can at least lift it high enough to stop more water flowing from the AC unit when I need to, though. I also tried using a snake, it went down about 8 feet and just stopped since the pipe makes a 90 degree turn there, I couldn't get it to go further, the blockage is past that.

I've attached a diagram showing how my plumbing is configured from what I can see when I'm in the attic. The smaller white pvc pipe empties into the larger black plastic pipes at point B, and this is where the water is overflowing. Point A is higher than B, I'm guessing that's the vent pipe and the vertical pipe to the right is the vent stack? I just googled this stuff, I know very little about plumbing. I'm not sure if the blockage is somewhere near point C or further down by D or further past that. I can't see what happens below point D and E but I'm guessing those 2 points connect again down there somewhere. There's a 2nd floor bathroom with a bathtub just a few few away from point E, I assume the tub connects there somewhere. I'm wondering if the blockage was much further down from point D, and if all these pipes were connected, would I also get water overflowing into the tub since it's at a lower point than this point B?

Anyhow this just seems like a terrible design. The only way to know if your pipe is clogged is to wait until water damage is done to your ceiling? I'm wondering if anyone has more suggestions for me before I call a professional, and I'm also wondering what kind of professional to call? If I do call someone out I'm thinking instead of calling someone to unclog the drain, I'd rather have someone to reroute the pipe and let it empty outside the house, I do have flowerbeds outside, I could use that water for irrigation. But then it seems like it would be odd to have a drain outside the house constantly outputting water like that, I haven't really seen anyone other homes with something like that. It seems so wasteful for this water to just be dumped into the drain when it could be reused, why are these AC drain systems designed this way?

 

[Gary]

A regular routine of bleach down the condensate drain works. Or you could have a small lift pump installed to pump the water to a drain.

 

[pjones]

So when you put the baking soda and vinegar into the pipe that is clogged are you then covering the pipe to allow pressure to build up and push the blockage through?

 

[pjones]

You could have the drain go into a condensate pump that has an overflow safety switch incorporated into it. The pump would push through the drain with positive pressure and if it failed or became blocked them the water would rise and trigger your safety switch.

Wire your air conditioning control wire through that safety switch so that it turns off the air con when it trips.

If your furnace dumps condensate also when it runs then run the control circuit power source through the safety switch and causes the whole system to shut down upon a high water event.

 

[EdInKentucky]

It is a terrible design.

Terrible enough that if it were my house, I'd move the ac air handler out of the attic, down into some sort of alcove in the living space.

Still better, install a new, clean air handler, with a MERV 8 or better "media" filter setup.

What you're experiencing is the best reason to NOT install ANY equipment into an unheated/uncooled difficult-to-reach attic.

Move the air handler, and use an automatic pump, with an overflow safety switch ... to move the condensate water to a remote place.

A basement sump pump, a laundry machine drain, sometimes outdoors, a laundry sink ... all are ok disposal places.

Be careful if you try to re-use ac condensate water ... it contains a lot of bacteria from the air that passes through the air handler.

Also, moving the air handler will give you the opportunity to upgrade the ducts in the attic, if they're too small, are leaky, and/or have thin, cheap insulation.

And always get your ac system checked every spring, by a trustworthy licensed professional.
That's cheap insurance.

Like it or not, a/c equipment requires regular maintenance.

 

[Sparky617]

Around here most homes have an attic unit for the second floor and a basement or crawlspace unit for the first floor. It keeps the duct runs shorter, doesn't eat up space in the walls for ducts between floors and it is unlikely you'll have both units fail at the same time. Regular maintenance is key, including a little bleach down the drain to keep the algae growth at bay in the trap.