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  1. #1
    Join Date
    Sep 2015
    Location
    Seattle
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    Mini split condensate line into downspout freezing

    I live near Seattle and had a Daikin mini split system installed about 4 years ago. During that install, the drain line from two of the wall units was connected into a downspout a few feet off the ground. This works great during the summer, but we've had a major issue last year and this year during the winter.

    When the downspouts partially freeze but there's some snowmelt from the roof, the water starts backing up into the condensate drain and then comes out through one of the mini splits. This is obviously not ideal.

    Can anyone provide any suggestions on options to fix this? A few things I've thought of:
    1. Disconnect the drain tube from the downspout and route it elsewhere. The issue is that there's a gravel path right along the house there so this is not the best solution.
    2. Add a check valve or even just a simple valve I could close for the winter, but freezing temperatures would likely break anything simple there.

    Any help/advice would be greatly appreciated!

  2. #2
    Join Date
    Mar 2005
    Location
    burlington county n.j.
    Posts
    9,880
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    Maybe some type of air gap between drain line and downspout so it can’t back into the house.

  3. #3
    Join Date
    Sep 2015
    Location
    Seattle
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    5
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    Thread Starter
    An air gap would be great, but I can't think of a way to do that without the backing water just going out the side of the downspout and onto the side of the house. Better than inside the house, but still not great.

  4. #4
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    27,291
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    Frozen downspouts yet your running the A/C ?

  5. #5
    Join Date
    Sep 2007
    Location
    edmonds wa
    Posts
    4,434
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    Either a grow room or Bitcoin mining. Heat trace the line, or open the window.
    UA Local 32 retired as of Jan 2020

  6. #6
    Join Date
    Mar 2005
    Location
    burlington county n.j.
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    9,880
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    I don’t see it as running a/c, just water from snow melt backing up drain line when downspout is frozen

  7. #7
    Join Date
    Sep 2015
    Location
    Seattle
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    Thread Starter
    Hehe, nope, no grow room or bitcoin mining. The mini split is running, but it heats the whole house. As far as I can tell, there's no new condensate during the winter (and I wouldn't expect any). This is purely backup from the downspout.

    Basically, does anyone know of a way to either air gap a drain line running into a downspout, or put in a frost-proof check valve (or something that functions as one).

  8. #8
    Join Date
    Sep 2007
    Location
    edmonds wa
    Posts
    4,434
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    Maybe just heat trace that downspout then, some models are made to drop down the pipe from the top and have a self regulating output along with a thermostat.
    UA Local 32 retired as of Jan 2020

  9. #9
    Join Date
    Mar 2018
    Location
    Chico, Ca #StateofJefferson
    Posts
    1,883
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    What's the problem with draining it into some bushes along the side of the home?

  10. #10
    Join Date
    May 2006
    Location
    Austin, Texas
    Posts
    576
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    Instead of draining into downspout, run drain down exterior of downspout.

  11. #11
    Join Date
    Sep 2015
    Location
    Seattle
    Posts
    5
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    Thread Starter
    Unfortunately heating the downspout wouldn't directly help - I'm guessing the water gets backed up from where it drains into a rain garden. I'm assuming some snow there will blocks up the end of the drain and starts the freezing process.

    Also no good place to dump the water there. We have a four foot wide gravel path right along the house and it's all uphill from there. I can route it to where the condenser it, but it'll be a pain to get around the downspout.

    In the meantime, I have a temporary solution that might turn into a permanent one. I've added a PVC tee between the downspout and where the drain line enters the house. Normally, I can keep it plugged so that water from the drain line flows into the downspout. When freezing weather and snow are expected (1 or 2 weeks out of the year), I can open up the plug and let water coming up flow out. Not ideal but should hopefully do the trick. Only issue is I'll probably need to wait for next winter to see if it works given how rare it is for us to get snow and extended periods of freezing.

    Thanks everyone for your suggestions!

  12. #12
    Join Date
    Mar 2005
    Location
    burlington county n.j.
    Posts
    9,880
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    That should work

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