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Adam81
Re: Dripping sound in ducts

I came across this thread and wanted to post, as I am having a somewhat similar issue.

In the last week, I have noticed a dripping/clicking sound coming a specific, narrow wall near the front of the house. Basically, when you walk in the house it is the wall that separates the hallway from the kitchen. It is a ceiling-to-floor wall, height-wise, and is maybe half a foot wide with a depth of two feet or so.

Anyway, I hear a loud series of clicks or drips in the wall maybe 30 seconds or so after the central air conditioning comes on. There will be between 10 and 20 clicks like this at 5 to 10 second intervals, at which point they get less frequent until the ac shuts off.

After the ac has been off for a minute or so, I will again hear several clicks in this wall at short intervals, which then taper off to being less and less frequent until the ac clicks on.

At first I thought this was dripping, but when I press my ear right up against the wall it sounds more like an aluminum clicking or popping sound. And again it is confined to this one wall, which is at the front of the house while the ac unit is in the back yard.

Any thoughts as what could be happening?

A. Spruce
Re: Dripping sound in ducts
Adam81 wrote:

Anyway, I hear a loud series of clicks or drips in the wall maybe 30 seconds or so after the central air conditioning comes on. There will be between 10 and 20 clicks like this at 5 to 10 second intervals, at which point they get less frequent until the ac shuts off.

After the ac has been off for a minute or so, I will again hear several clicks in this wall at short intervals, which then taper off to being less and less frequent until the ac clicks on.

Normal thermal expansion and contraction of the duct within the wall. Metal at ambient temperature makes no noise, heat or cool that metal and it will either expand or contract, this movement is what is causing the clicking/dripping sound. Also, the sound can be more pronounced where it is touching framing or the back of drywall, etc. You've got one surface moving against a stationary object, you're going to get friction and noise.

Adam81
Re: Dripping sound in ducts
A. Spruce wrote:

Normal thermal expansion and contraction of the duct within the wall. Metal at ambient temperature makes no noise, heat or cool that metal and it will either expand or contract, this movement is what is causing the clicking/dripping sound. Also, the sound can be more pronounced where it is touching framing or the back of drywall, etc. You've got one surface moving against a stationary object, you're going to get friction and noise.

Thanks so much for the quick reply! That definitely puts my mind at ease, particularly that it is normal expansion/contraction rather than a water drip. Thanks again.

Adam81
Re: Dripping sound in ducts
Adam81 wrote:

Thanks so much for the quick reply! That definitely puts my mind at ease, particularly that it is normal expansion/contraction rather than a water drip. Thanks again.

I just wanted to follow up here with further confirmation of the expansion/contraction issue as the culprit of my issue. Last night we turned the AC off completely and I did not hear those sounds at all for the duration of the evening and overnight hours. Thanks again!

Erik
Re: Dripping sound in ducts

I have been over this thread several times and still can't seem to solve my issue. If anyone has any new updates or advise please advise. Every night when our furnace runs there is a dripping sound coming from what appears to be the flue. Our bedroom is on the second floor and the a joining bathroom has a section of wall where the straight flue runs up and exits the roof through the attic. The noise keeps us up at night but seems to dissipate when the furnace is off for awhile. When you put your ear to the wall you get a combination of dripping sounds as well as other clicking sounds, but it's within that vertical run. Drives my crazy every night.
Thanks

A. Spruce
Re: Dripping sound in ducts
Erik wrote:

I have been over this thread several times and still can't seem to solve my issue. If anyone has any new updates or advise please advise. Every night when our furnace runs there is a dripping sound coming from what appears to be the flue. Our bedroom is on the second floor and the a joining bathroom has a section of wall where the straight flue runs up and exits the roof through the attic. The noise keeps us up at night but seems to dissipate when the furnace is off for awhile. When you put your ear to the wall you get a combination of dripping sounds as well as other clicking sounds, but it's within that vertical run. Drives my crazy every night.
Thanks

Same answer for you as throughout this thread, heat expansion and contraction of the flue will make it click and pop, especially if it is held tight against framing somewhere. There is nothing you can do about the flue noise itself, however you can isolate it from framing if there is any contact anywhere.

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