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  1. #1
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    Default furnace condensate and sump pump

    Is there a problem discharging high efficiency furnace condensate into a sump, due to the caustic nature of the condensate damaging the pump?

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  2. #2
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    Default Re: furnace condensate and sump pump

    John,

    I am sure you can find a sump pump rated for all kinds of fluids, just not sure is a standard condensate sump and pump are.

    Did you get the manufacturer of the condensate sump which was installed?

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  3. #3
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    Default Re: furnace condensate and sump pump

    Quote Originally Posted by Jerry Peck View Post
    John,

    I am sure you can find a sump pump rated for all kinds of fluids, just not sure is a standard condensate sump and pump are.

    Did you get the manufacturer of the condensate sump which was installed?
    Actually, I started wondering while listening to a plumbing webinar. I wasn't satisfied with the answer from the presenter because he characterized furnace condensate as "water vapor" and therefore harmless to a pump. He was saying that caustic fluids, like bleach from a laundry tub, should not discharge into a basement sump pump (of course), and I asked about condensing furnaces because I see them discharging into sump pumps all the time. Sump pumps. Not condensate pumps.

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  4. #4
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    Default Re: furnace condensate and sump pump

    Discharging into the sump does two things that are a negative.

    1. Adds moisture to below slab.
    2. Requires more electricity to cycle on and off.

    A condensate pump with discharge outside the home is my preference.


  5. #5
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    Default Re: furnace condensate and sump pump

    Condensate from high efficiency furnaces is slightly acidic, about the same as Coca-Cola.

    Some of these furnaces will have a block of neutralizing substance in the condensate drain system. Others do not. It should not harm your sump pump if its mixing with other water in the pit.


  6. #6
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    Default Re: furnace condensate and sump pump

    John, I questioned the same response as well (I was in on that webinar also) from him. I always thought that the condensate from a high efficiency furnace was corrosive as well, but after reading Ray's response I'm inclined to side with him. I have never called this out before and I don't think I will (unless someone else has more compelling evidence). Furthermore, I don't have a problem with washing machines dumping into them also (speaking here on experience).

    RJDalga
    http://homeanalysts.com
    Kalamazoo, MI

  7. #7
    Daniel Leung's Avatar
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    Default Re: furnace condensate and sump pump

    Quote Originally Posted by Raymond Wand View Post
    Condensate from high efficiency furnaces is slightly acidic, about the same as Coca-Cola......... It should not harm your sump pump if its mixing with other water in the pit.
    Agree! Based on my working experience of wastewater treatment. Small amount of corrosive condensate mixed with other water in the sump is no harm to the "sewerage" pump (not "water" pump) with good ventilation to exterior.


  8. #8
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    Smile Re: furnace condensate and sump pump

    I call dumping the furnace condensate into a sump a "dope slap!" There is seldom enough condensate to lift the float and activate the pump. The condensate evaporates back into the home not a bright thing to do, but convenient for installers. I also get a kick out of the homeowners who drain the dehumidifier into the sump. I always recommend that a condensate pump be installed for discharge to the exterior.


  9. #9
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    Default Re: furnace condensate and sump pump

    I can't see the acidic content of condensate water damaging a typical sump pump, especially once it's diluted with water that's in the sump pit. The standard condensate pumps are fairly cheap plastic contraptions. If the condensate doesn't eat those it isn't going to eat a sump pump.
    As far as energy usage from the sump kicking on, I don't see that as an issue on the heat side. Maybe on the AC side if it is also pumped to the pit but doubtful.
    Besides a new sump pump is cheap.

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  10. #10
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    Default Re: furnace condensate and sump pump

    In one of my trade magazines there was an article about how corrosive condensate was from the condensing heaters. It showed a condensate drain that was draining into a near by floor drain for only a couple months and the brass ring for the floor drain and the concrete around the drain where badly etched.

    I will try to find this article and post it here.


  11. #11
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    Default Re: furnace condensate and sump pump

    Still cannot find the which trade magazine had the article but this post came up on the ridgid forums. Copper pipe corrosion on a condensing furnace - RIDGID Plumbing Forum, Woodworking Forum, Power Tool Forum


  12. #12
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    Default Re: furnace condensate and sump pump

    Quote Originally Posted by Ken Amelin View Post

    A condensate pump with discharge outside the home is my preference.
    If the conditions outdoors are below freezing for any extended period of time this is going to create more of an issue than discharging into a sump.

    Measured Performance more than just a buzzword

  13. #13
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    Default Re: furnace condensate and sump pump

    Dave,

    Agree about the freeze potential, but it is all about installation details. If it's a 3/8 inch plastic hose that sticks out of the band joint then Yes, it will freeze. If it is a 3/8 hose that is run within a 1" inch PVC pipe that elbows to the ground, not a problem.


  14. #14
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    Default Re: furnace condensate and sump pump

    I installed a standard condensate pump when installing my 90+ gas furnace about 8 years ago. No problems so far.


  15. #15
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    Default Re: furnace condensate and sump pump

    Quote Originally Posted by Trent Tarter View Post
    I installed a standard condensate pump when installing my 90+ gas furnace about 8 years ago. No problems so far.
    You've been lucky Trent.

    Is the drain terminated outdoors?

    Measured Performance more than just a buzzword

  16. #16
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    Default Re: furnace condensate and sump pump

    No the drain terminates indoors.


  17. #17
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    Default Re: furnace condensate and sump pump

    Quote Originally Posted by fritzkelly View Post
    CH4 + (3)O2 yields CO2 and (4)H20. Where's the acid?
    Problem is the PH level of the water. its very acidic. I am still digging through all my trade magazines for the article. Basically in the end they showed how to make a condensate neutralizer.


  18. #18
    Daniel Leung's Avatar
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    Default Re: furnace condensate and sump pump

    Quote Originally Posted by fritzkelly View Post
    CH4 + (3)O2 yields CO2 and (4)H20. Where's the acid?
    Oh, I almost forgot what I learn 45 years ago. When the Methane CH4 (in the natural gas) burns with Oxygen O2, it forms Carbon Dioxide CO2 and Water H2O (ref: Methane - Wikipedia, the free encyclopedia
    CH4 + 2O2 → CO2 + 2H2O
    This chemical reaction is not complete yet. If the Carbon Dioxide disolved into the water, it forms Carbonic Acid H2CO3, a weak acid H2CO3 - It is used in making of soft drinks eg. Colas, Ice Tea, Lemonade and Sparkling Water (ref: Carbonic acid - Wikipedia, the free encyclopedia
    CO2 + H2O ⇌ H2CO3

    Last edited by Daniel Leung; 08-23-2009 at 11:12 PM. Reason: correct the wikipedia links

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