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  1. #1
    Join Date
    Nov 2009
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    2

    Default Dripping sound in ducts

    I have a new home (first owner), forced air heat. After the furnace runs for a bit and then shuts down, there is a distinct dripping sound coming from the celing. There are no water pipes there...just the air ducting. I am told this could be condensation forming in the ducts. If this is the case....should there be condensation forming in the ducting? does the build up of condensation lead to problems down the road (mildew, mold, etc) that I should be concerned with? is there a resolution to the very annoying drip sound that I should expect the builder to employ in order to fix this issue?

  2. #2
    Join Date
    Jul 2009
    Location
    Northeast
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    Default Re: Dripping sound in ducts

    Are you using Heat or A/C? If your Duct work is not insulated and your using the A/C and you are hearing dripping sounds more than likely it is condensation. It forms due the cold air in the ductwork and warm or hot air in the attic or cellar the Ductwork is in. Your ductwork should always be insulated be it heat or A/C to reduce temp loss, gain and condensation. I guess over time it is possible for mold to form. An easy check is to go in the attic and see if your ductwork is insulated, I would think that a responsible HVAC Contractor would do this but you never know. Good Luck!!!

  3. #3
    Join Date
    Aug 2007
    Location
    The Great White North
    Posts
    4,045

    Default Re: Dripping sound in ducts

    Quote Originally Posted by jacushion View Post
    I have a new home (first owner), forced air heat. After the furnace runs for a bit and then shuts down, there is a distinct dripping sound coming from the celing. There are no water pipes there...just the air ducting. I am told this could be condensation forming in the ducts. If this is the case....should there be condensation forming in the ducting? does the build up of condensation lead to problems down the road (mildew, mold, etc) that I should be concerned with? is there a resolution to the very annoying drip sound that I should expect the builder to employ in order to fix this issue?
    It could also be the sound of the metal ducting expanding and contracting.
    You may not hear the expansion noise when the furnace is on due to the velocity noise masking the sound ------but you will more likely hear the contraction when the furnace shuts off since there are no other sounds to mask this noise.

    Just a thought.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  4. #4
    Join Date
    Nov 2009
    Posts
    2

    Default Re: Dripping sound in ducts

    Sten/Canuk...thanks for your ideas. I only have heating (no a/c) so the dripping sound is isolated to post-heat runs. The ducting seems pretty well insulated and I have spent quite a few months trying to convince myself that the sounds I am hearing are the expansion/contraction of metal...unfortunately the sound is just too similar to a faucet steady drip. It has also been suggested that this is from a run-off pvc pipe from the condensation drip pan (not sure that is the correct terminology)...so I am off to check that theory

  5. #5
    Join Date
    Jun 2007
    Posts
    74

    Default Re: Dripping sound in ducts

    I'm opening up this old thread in the hopes of getting some new answers. I also have some additional info from my own similar situation.
    My last house was 27 years old when we bought it. It had floor vents and the ducts were rigid metal (galvanized, I suppose). They were insulated and ran through an unconditioned basement. We had the drip sound in only one room. It was not there when we moved in and after it started it got worse every year. (We sold the house after 5 years.) It only happened with heating, not cooling. I tried "superinsulating" the one duct and it made no difference. The individual duct that fed that room was only about 10 feet long and I ran a rag down into it on a stiff wire, looking for moisture. As I recall, I couldn't make the whole distance but, then again, the "drip" sounded like it was pretty close to the vent. I didn't find moisture regardless. I also checked for moisture at the damper and there was none coming out. Unlike the OP, I could hear the sound even when the air was running and it usually quit when the air shut off; that made me think it was not a drip but it really sounded like one.

    We bought this house less than 3 months ago; it's 42 years old. Again we have floor vents but this time the ducts are uninsulated metal and they're running through a conditioned basement. We have the drip sound in most of the rooms, and it's as bad as in the last house at the time we sold it. I realize right now that I don't know how the sounds in this house correspond to the air running or not; but I'll find out and post that.

    jacushion, if you're still here, I'd be interested to know if you have rigid or flexible ducts.


    I hope somebody has info on this.
    thanks
    Last edited by johnL; 12-23-2010 at 10:35 PM.

  6. #6
    Join Date
    Jun 2007
    Location
    West Jordan, Utah
    Posts
    84

    Default Re: Dripping sound in ducts

    The last house that we lived in had the same drip noise that you are hearing. I was able to isolate the sound to the exhaust vent that ran up through the roof. Some of the moisture in the exhaust was condensing in the cold part of the vent and on the vent cap and then would drip down to the bottom of the vent. I changed the vent cap and most of the noise went away. We still had an occasional drip but not like it was.
    Slow The Flow

  7. #7
    Join Date
    Jun 2007
    Posts
    74

    Default Re: Dripping sound in ducts

    Are you talking about the chimney from the furnace?
    Thanks for the reply.

  8. #8
    Join Date
    Jun 2007
    Location
    West Jordan, Utah
    Posts
    84

    Default Re: Dripping sound in ducts

    Yes, The vent pipe that ran straight from the basement up through the roof, there is a cap on the bottom of the vent that the drips would hit and the sound could be heard through the ducts.
    Slow The Flow

  9. #9
    Join Date
    Jun 2007
    Posts
    74

    Default Re: Dripping sound in ducts

    Okay, thanks for that info.

  10. #10
    Join Date
    Mar 2010
    Location
    Canada
    Posts
    86

    Default Re: Dripping sound in ducts

    I'm hearing that sound as I type and it's as Canuk described.
    The metal ducting expands from the heated air flowing through and when it cools it contracts. In other words, the ducting moves and also rubs along any lumber or hangers it contacts, the metal boots at the floor opening moving on the nails used to fasten them in place, the main trunks and so on. In cases some HVAC installers will also install a flex joint at the main plenum takeoff to absorb some of the movement as well for sound control.
    As for the sound from dripping condensation in the exhaust flue , that's a strange one. I'm trying to figure how that sound can travel from that point all the way through the heating system , distrubution trunk and to the furthest part of the network.

    Merry Christmas

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