knocking in heat ducts

Old 04-07-05, 01:05 AM
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knocking in heat ducts

We have a 3-level townhome with forced air heating. For the past few days there has been knocking and ticking/clicking sounds thru the heat registers. It's the knocking that's worrying me

What is this? Anybody know? What can I do to get rid of it?

Thanks in advance,

Old 04-07-05, 06:35 AM
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Noisy Ducts

Nikkil --

We as well as most others in our region have forced air heating and air conditioning. In our case, the noise (clicking, tapping, thumping sounds) is caused by the continuous contraction and expansion of the metal ductwork. (heat expands; cold contracts) When warm forced air flows through the metal duct work, it will cause some expansion. And when it begins to cool a little, it will begin to contract. The contraction and expansion process of the metal produces a noise. According to my heating and A/C contractor, even if you have flex-duct (non metal), the "boots" that connect the flex-duct to the heating registers are made of metal and will expand and contract and produce a noise. He says nothing practical can be done about it.

Of course, some experts will probably come on the forum refuting everything I have written. However what my contractor told me sounds logical.

If that's not what is making the noise, it's probably a ghost.
Old 04-07-05, 07:44 AM
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Well like said in a way. But you have to try and find out Just where it is and start there. There are flex duct connectors you can use in the duct work .Lots of times if you drill and put sheet metal screws in the slips there on the duct where two duct come together. Some times cut down on the on and off temp of the blower. Somes times hit it with a hammer and put a small dent in the duct. Change the blower speed. And on and on but you have to like find it first.

Old 04-19-05, 05:52 AM
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Clicking and popping in the air duct

Hi Ed & members -

I found this string through Googling this problem. My fiancee and I purchased and moved into a brand new, never-lived in house that was built about 6 months ago. We've been living in this house for about 3 weeks. During our first week in this house, we noticed knocking sounds coming from the walls when turning on the hot water and a clicking sound when we would turn on the hot air (the noise could be heard in our bedroom vent). We have not gotten much sleep as a result of these sounds.

The warranty for this house says that it is covered for "structural defect". Do these sounds qualify as structural defects, in your opinion? We've had several people come (the plumbers and the HVAC person who did the original work), and they put big holes in our walls and concluded that they couldn't do anything else. When we would approach the seller about these issues, her response is that the house passed all city code inspections, and these problems are not her obligation to fix.

My fiancee and I are small in stature, but we would love to learn of any ways to fix these problems ourselves if that is at all possible. If anyone can direct us as to how to fix these problems, nothing would thrill us more at this point!

Old 04-20-05, 03:02 AM
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iamgracepark :

I'm not a contractor, professional handyman, etc. I'm a longtime homeowner and over time I've had numerous experiences with this and that.

In ductwork, especially if its made of metal, you will sometimes hear an inconsistent clicking and tapping due to the contraction and expansion of the metal ductwork. When warm air is flowing, the ductwork will have a tendency to expand. When it cools, it will contract a little causing a snapping and clicking sound. See related posts above. Imaduc tells how this can be remedied. Most ductwork nowadays is flexduct and not made of metal.
However the boots (couples the flexduct to the floor registers) are usually metal.

With regard to your clicking and tapping sound when you turn on your hot water: A few years ago I had a similar problem. Whenever water was turned on and flowing through the pipes we would hear the tapping, thumping and banging sound (not just when hot water was on, but any water flow caused it to make that sound -- it was more pronounced when the clothes washer was taking on water and when a toilet was flushed. I discovered the problem was some loose clamps that are used to clamp the water pipes tightly to keep them from vibrating. One lose clamp was underneath the crawl space and easy to fix. The other was inside the drywall and was a hassle to get to.

On a separate occassion, I would hear a steady ticking and clicking noise everytime water was being turned on. I asked my plumber about it. He said that 95 percent of the time, when you hear a steady ticking and clicking sound like that, it is the water meter itself. He explained that old water meters have a "worm gear" which becomes worn and consequently the water does not flow evenly through the meter. This uneven flow of water causes the incoming water to bump and jerk along inside your pipes causing an annoying clicking sound. (Is your water meter on the curb?) He told me to call my water company and tell them to replace the meter. He also warned me that the water company would not want to replace the meter, so I should be aggressive and sound like I knew what I was talking about. I did so. The water meter was replaced. Problem solved. Probably nothing that I have hastily written will be of any help to you, but it might. Check it out. Of course, and as always, some experts are gonna show up on this forum and say I don't know what I'm talking about -- I'm just relating my own personal experiences. In closing, I just want to mention that if water pipes are not firmly clamped to keep them from vibrating, they'll eventually get looser and looser (pardon grammar) and might break. Best of luck.
Old 04-20-05, 03:50 AM
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Hi Nonsohandy -

THanks for imparting your experiences. We have a forced air system with hard ducts and metal boots - I'm seriously considering taking Ed's advice and putting a dent in it

As for the water pipes, the plumber who came yesterday said it might be the same type of issue... expansion and contraction of hot water supply pipes. So he said he would have to explore all of our pipes (cut out all the drywall that covers the pipes) and find the problem joints and either loosen or tighten them. But your explanation seems plausible too... and there might be a loose clamp somewhere and over time the pipe will break. I don't think it's the meter however because the meter is on the side of the house and it is brand new like the rest of the house.
Old 04-20-05, 02:33 PM
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Well most hvac contractors give a 1 yr. labor warranty. I give a warranty on duct work for the life of the furnace. As to materials and workmanship. Just get in contact with your contractor they are normally reasonable people and some fixes are not much.
Old 04-21-05, 03:06 AM
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our contractor

was actually not very reasonable. He was the guy who built the whole thing, but when we asked him to see it, after hunting after him for 2 weeks, he finally came 2 hours late. The next time he came with the builder of the house, they were supposed to meet us at 7:00PM and showed up at 10:00PM. Next day, when they agreed to fix it at 3:00PM, my fiancee ran home from work to meet them... they didn't start work until 6:30PM. They cut out the drywall covering the boot of the duct that connects to the register and insulated the whole thing. When that didn't work, the contractor got really upset at us for complaining about "normal operational sound" which this clearly is not because it wakes us up at night and all the other vent registers don't make this sound. We asked him to leave and he threatened us on his way out.

Sorry about venting... this guy is not going to fix anything for sure. And even if he was, I want to see his certification from an anger management school before I let him into the house! At this point, we don't really trust anyone - that's why I'm here on the forum, trying desperately to get ideas to possibly fix it ourselves.

Thanks in advance for any suggestions.
Old 12-28-13, 10:03 AM
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Two options for fixing

I had issues in my new house with a few of the ducts popping and knocking when the heat was running. The first duct with the issue was in the first floor and I had direct access to the duct through the basement ceiling. I scored the offending area first with a blade, then took a hammer to it to VERY slightly dent it. The dent provides a bit of expansion room to alliviate the pressure on the spot that is causing the noise. There is no longer any noise in the 'fixed' spot.

Another solution is to put a piece of cardboard between the duct and whatever it is rubbing on, if you have access to the area and if you can find the problem spot.

The other vent that is popping in my house is in the top floor. I do not have direct access to the exterior of the duct. Fixing this one will be more of a challenge. My plan is to do the dent method, from the inside of the duct. There is not much room to work with for creating a dent with a hammer, but in theory the approach should work.

Good luck!
Old 02-21-14, 06:01 AM
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Qix_fix- did your inside duct dent method work?

Qix_fix- did you try your inside dent method and have any success in actually creating the dent or easing the tinging?

I of course have the same issue but I'm willing to bet mine is significantly louder than most! I had a technician (family member) come over and check the hookup of the furnace with fan speed, temp settings, etc and he configured best he could with fan constantly running to ease the heating and cooling and see if that worked. Well, it didn't and that clicking/tinging sound that repeats itself as I lie trying to fall asleep is like nails on a chalkboard to me by this point.

I do have a rather larger furnace for the size of my house but is an efficient variable speed one. Suggestion was made that maybe a smaller furnace COULD ease the problem, but is that really a guarantee or just an expensive risk to take!?!?
Old 02-21-14, 06:37 AM
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