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Thread: How to clear up my HVAC drain?

  1. #1
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    How to clear up my HVAC drain?

    My furnace, A/C, and humidifier all drain into a hole in the floor.
    A few days ago I had a minor flood. Turning off the humidifier and cleaning up, I determined it was from the humidifier. I turned the humidifer back on to see how it was leaking, and found it was at the drain.
    It has been fine for 15 years; how do I clear it?

    The ground is very wet now, but I am sure it has been this bad sometime in the last 15 years. The house has two sets of drain tiles that gravity feed to the lake 15 feet below the level of the walk out basement.drain.jpg

  2. #2
    Try a Gallo Gun on the portion of the drain that is blocked. It uses a CO2 cartridge and a plastic plug to block the inlet to the drain and blows it out.

  3. #3
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    Quote Originally Posted by Jack Frederick View Post
    Try a Gallo Gun on the portion of the drain that is blocked. It uses a CO2 cartridge and a plastic plug to block the inlet to the drain and blows it out.
    Water that goes down the pipe comes out the hole in the floor. Wouldn't the CO2 do that also?

  4. #4
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    Why does a humidifier have a drain? Do you mean dehumidifier? When you say it leaks "at the drain", what do you mean? Is the drain pipe from the (de)humidifier unit leading to the floor drain pipe leaking or is the drain pipe in the floor backing up?

  5. #5
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    Snake. You may have to cut it and install a fernco tee for access.
    If you mean the ground is saturated you should probably move over a few feet and drill a new dry well. Septic fields only last so long before they must be redone.
    Bill D

  6. #6
    My Aprilaire humidifier has a drain that runs from the humidifier to the laundry sink. It gets clogged with slime occasionally and has been blown out with air by the HVAC company, or more recently I have been sucking it out with a wet dry vac. Not sure if that helps.

    Sounds to me like your problem is in the drain, not the humidifier drain line. If the humidifier line was clogged I think it would leak at the humidifier or furnace.

  7. #7
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    Snake the line. Rental places have them.

  8. #8
    Quote Originally Posted by Tom M King View Post
    Snake the line. Rental places have them.
    X2. If water is coming into basement turn the humidifier off until you clear the drain.

  9. #9
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    Quote Originally Posted by Doug Garson View Post
    Why does a humidifier have a drain? Do you mean dehumidifier? When you say it leaks "at the drain", what do you mean? Is the drain pipe from the (de)humidifier unit leading to the floor drain pipe leaking or is the drain pipe in the floor backing up?
    More water going into the humidifier than is evaporated. The excess goes down the PVC drainline into the hole in the floor. The ground isn't absorbing the water, so it comes up the hole.

  10. #10
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    Quote Originally Posted by Wade Lippman View Post
    More water going into the humidifier than is evaporated. The excess goes down the PVC drainline into the hole in the floor. The ground isn't absorbing the water, so it comes up the hole.
    Thanks for clarifying, seems like an odd design, any humidifier I've seen just has a level control and shuts off the water supply when the reservoir is full. If the drain in the ground is backing up because the ground is saturated, not sure what you can do to fix it other than reroute the humidifier drain into a sump and then pump it outside.

  11. #11
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    Not really relevant to the original question, but that pipe in the floor looks like it would be an incoming freeway for ants in dry weather.
    Yoga class makes me feel like a total stud, mostly because I'm about as flexible as a 2x4.
    "Design"? Possibly. "Intelligent"? Sure doesn't look like it from this angle.
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  12. #12
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    Update...
    The pipe itself is fine, so there is no clog to remove. The water just isn't soaking in from the cavity below the pipe fast enough. I tried pouring drain cleaner in, and poking it with a driveway marker, but they didn't help much.
    I replaced the humidistat this year. It is possible that it comes on at higher humidity than the old one. Since less water would evaporate at a higher humidity, it might just be sending too much left over water to the drain. Or, maybe the ground is just too saturated; there are puddles all over. I will leave the humidifier off for a few weeks and see if that actually help. If not, I guess I will have to figure how to fix/replace the hole.

  13. #13
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    Might need a condensate pump, to pump it up, and out somewhere else.

  14. #14
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    Quote Originally Posted by Tom M King View Post
    Might need a condensate pump, to pump it up, and out somewhere else.
    If it doesn't clear up in a few weeks, you might be right. I was in Lowes today; their condensate pumps specify they are not for high efficiency furnaces or humidifiers, which is what I need. Actually I don't need the high efficiency furnace... the drain can handle that even now and it would be easy to split off the humidifier. I don't know what is wrong with humidifier water; it is just water, perhaps with a slightly higher mineral content.

    Is there anyway to restrict the flow of water coming over the 1/4" tube going to the humidifier? It certainly doesn't need all the water it is getting; at least not now. Can I simply not open the quarter turn valve all the way? Of course... once the filter starts to clog up it will restrict itself.

  15. #15
    Quote Originally Posted by Wade Lippman View Post
    If it doesn't clear up in a few weeks, you might be right. I was in Lowes today; their condensate pumps specify they are not for high efficiency furnaces or humidifiers, which is what I need. Actually I don't need the high efficiency furnace... the drain can handle that even now and it would be easy to split off the humidifier. I don't know what is wrong with humidifier water; it is just water, perhaps with a slightly higher mineral content.

    Is there anyway to restrict the flow of water coming over the 1/4" tube going to the humidifier? It certainly doesn't need all the water it is getting; at least not now. Can I simply not open the quarter turn valve all the way? Of course... once the filter starts to clog up it will restrict itself.
    When I had a problem with my humidifier line to the sink clogging, my HVAC guy recommended a condensate pump. I didn't like that idea because I feel the heavy use could cause it to fail and I thought I would be right back at square one. My humidifier as a much greater output than my central AC unit by far.

    BTW, Aprilaire recommends replacing the metallic pad once a year. I found that twice a year is better. in a full season it starts breaking down and small bits of it flow into the drain and add to my clogging problem.

    My humidifier is fed through a saddle valve on a copper pipe. I suppose the valve could be adjusted so the flow is less. Never tried it. I think the higher flow is designed in to flush the pad and drain line. I am not an HVAC man though.

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