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Old 08-25-2015, 07:50 PM   #1
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Gurgling in my AC primary drain pipe.


There is a vertical 3/4" pipe standing up on the pipe that goes from my Lennox 4 ton evaporator to the sink drain.(about a 20 foot run). Cold air blows out of it. It has been gurgling for a few weeks and has puked out water, enough to stain the sheetrock in the ceiling below. The pan under the unit is full and is draining outside the house. I figured the primary drain (the one to the sink?) was clogged up.

I detached the drain from the sink and no water drained out. I poured bleach in the stand up pipe and blew some air down there as well, then for good measure blew some up from the sink drain. Water started flowing. I got about two gallons before reattaching the hose to the sink drain. Then I removed the water standing in the overflow pan. I figured, done.

But now, a day later the gurgling continues. At the sink, it is loud. The overflow is again dripping out of the pipe out of the house.

What's happening? What should I do next?

puttster

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Old 08-25-2015, 10:44 PM   #2
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Gurgling in my AC primary drain pipe.


Probably plugged again. Sometimes you'll get a drain pan full of solids. Sometimes, bacteria will start to grow in the water causing almost a jelly to fill the pan. It'll blog up several times before you get everything out. Pour water down the pipe for a bit after you clear it. If you can, clean out the pan inside the unit. (usually not very accessible)

PS. Is this a new unit or has it been running for a few years?

Cheers!

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Old 08-26-2015, 05:12 AM   #3
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Gurgling in my AC primary drain pipe.


Yes, unit is three years old. Are you thinking the drain pipe to the sink has plugged up again? Maybe from goop coming out of the pan in the unit?

We are probably going to get a new coil. Hopefully cleaning out the pipes will be part of the deal.
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Old 08-26-2015, 07:16 AM   #4
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Gurgling in my AC primary drain pipe.


Yes.

Why are you getting a new coil? Usually last a lot longer.

PS. You'll have to mention it to the installer when they come. Most usually wouldn't even check it the drain.

Cheers!

Last edited by supers05; 08-26-2015 at 07:18 AM.
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Old 08-26-2015, 08:51 AM   #5
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Gurgling in my AC primary drain pipe.


It sounds like you can get to the end of the drain line, hook a shop vac to it tightly and let it run for 5 mins or so, should suck the gunk out of the line, usually works pretty good.
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Old 08-26-2015, 09:46 AM   #6
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Gurgling in my AC primary drain pipe.


This morning the gurgling is still loud, as heard from the sink where the drain is. However, the draining outside seems to have quit. I truned off the AC, opened the sink trap and put a bucket under there and then poured a quart of water into the vertical tube, as supers05 recommended. All of it drained down the pipe and into the bucket.

I am feeling pretty good about primary drain but concerned about the gurgling. What's causing it? Maybe it too will pass?

My new unit takes 2 lbs of 410a annually. Two outfits want to replace the coil, which is under warranty, for $1250 and $1300 respectively. Turns out the coils were poorly made and are subject to a class action suit according to www.evaporatorcoillawsuit.com.
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Old 08-26-2015, 07:11 PM   #7
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Gurgling in my AC primary drain pipe.


Quote:
Originally Posted by puttster View Post
This morning the gurgling is still loud, as heard from the sink where the drain is. However, the draining outside seems to have quit. I truned off the AC, opened the sink trap and put a bucket under there and then poured a quart of water into the vertical tube, as supers05 recommended. All of it drained down the pipe and into the bucket.

I am feeling pretty good about primary drain but concerned about the gurgling. What's causing it? Maybe it too will pass?

My new unit takes 2 lbs of 410a annually. Two outfits want to replace the coil, which is under warranty, for $1250 and $1300 respectively. Turns out the coils were poorly made and are subject to a class action suit according to www.evaporatorcoillawsuit.com.
If it's no longer draining out the secondary drain, then you're good. The gurgling may or may not stop. If you want it to stop, you can make sure the drain flows down, and doesn't partially trap any water. You won't get gurgling with a full trap or no standing water, only a partial trap. If the vertical part of the drain is teed off the drain and open to the air, it should only gurgle before that point. Otherwise it can gurgle at any point along the drain.

It gurgles slightly on my own unit, but it's not loud enough to bother me. Everyone has different tolerance levels.

As for the cheap evap coils.... It happens. Especially in these economics driven days. Good luck with the replacement.

Cheers!
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Old 08-27-2015, 07:38 PM   #8
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Gurgling in my AC primary drain pipe.


Gurgling has stopped. House is cooling better, too.

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