# How to reduce or stop duct "cracking/popping"?



## biggles

definitly in the heating cycle as you see...it's just expansion POP and cooling off contraction CRACK.if you have an area standing under the duct and here it the most...might need a hanger to tighten it up.to test this a 2 pieces 2x4 T and hammer it under the duct from the floor to support the area...move it around to see if you eliminate the pop/crack


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## hvac5646

last resort would be to dent the supply in the area of the expansion noise.
post some pictures and we can give some comprehensive solution once we see exactly what it looks like.


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## harleyrider

I have found over the years that the best way to reduce or in some cases eliminate this type of noise is to "relax" the trunk line.........we do this by strapping the duct system up......then undoing ALL the original hangers.... and then re- attaching them.Most of this noise is caused by a structure settling over the years and putting tension on a trunk line as it does.......by UN attaching and re-attaching you relieve the stress.This really does work, we have done it many times.


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## yuri

You can also just go push it up and down from underneath in a bunch of places and it may settle into a new happy quiet space. If not then loosening and redoing the hangers may help. Get the wife to turn the heat on and off while you stand under the duct to see where it is coming from is necessary.


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## hvac5646

You guys are doing it the hard way...just use one'a these and show BaBa or Pierre where to smack the duct...last resort as I said.
_*...DA' ...WHERE DOES I HIT IT , YURI???

*_


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## yuri

Isn't it supposed to be Bubba and Pierre? In Quebec it is Pierre where I am we just use Pete.

Now that is what we call a tin basher.:laughing:

Now this looks like a fun place for Bubba and the Boyz. Saw it on my favorite show about those hog hunters.

http://redneckyachtclubmudpark.com/


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## hvac5646

He does the tear outs between wrestling dates:thumbsup:


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## Tator1076

I say check the filter first. If a dirty filter can cause duct work suck in when fan is on and when stop then pop. Even those thick dense filters can cause that too. May have to put in a cheaper air filter.


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## moneymgmt

went down there tonight, really notice it a lot more from the other side of the floor! 1st pic is the main trunk coming across the house to the bedroom (the corner we're facing). 2nd pic is the end of the trunk that makes the loudest and most repetitive noise. 3rd pic is another register in the bedroom that throws a lot of noise, it is in the far corner of the 1st pic. Last pic is bedroom on the other end of the house, its a spare room so I never pay attention to it but being in the basement it is one heck of a loud pop as it cools off. 

Thanks for all the feedback, sounds like I need to go and play with the joints and strapping and see where we get.


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## REP

The last time i incountered a house with the problems you discribe,The ductwork was too small.You could actually see the duct swell when the furnace started and relax when the furnace shut off.On this house the return was worse than the supply as the ra duct sucked in on startup and relaxed on shutdown.I increased the ductwork ,I added flex duct connectors and the noise was all gone.
Homeowner said they don't know how they lived with ity for 3 years.If the limit didn't go awol they would still be awakened in the middle of the night.


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## how

A number of my clients who have decided to run the furnace fan continuously to help with air filtration for allergies or to overcome a poor heat distribution layout list the quieting of the formally oil caning ducting as a side benefit.


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## yuri

if you find a section that is actually moving/being inflated etc you may end up reinforcing it as the metal they use now is as thin as possible. get a piece of angle iron or the stuff they make shelves from in warehouses and screw it to that section. pros use a piece of s cleat which is three layers thick and you can get it at a sheet metal shop. HDepot has aluminum and steel angle iron/metal in the screws and hardware section.


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## moneymgmt

It may have been a filter issue previously but I put in a new filter the day we moved in (5x16x25). The old one looked like a knit sweater, I've never seen one so bad before. 

Thanks for the feedback. I'll do some playing around with it this weekend and see if we get anywhere.


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## hammerlane

I can't give any suggestions on the duct banging but your basement and and ductwork is very similar to mine.

Take a few hours one day and get some silver duct tape and wrap all your joints like the photo I attached. Or you can use mastic on the joints.


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## hvac5646

DA...'EY, YURI, WHEN DO I GETS TO SMASH 'D DUCK' ALREADY???


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## jenbury

*popping in heat duct.*

Hello all, I've read all of your responses and they are very helpful. I unfortunately have this issue in a furnished basement with no access. Does anyone have any tips for this situation that don't entail tearing out a finished ceiling? appreciate your responses.


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## j cat

jenbury said:


> Hello all, I've read all of your responses and they are very helpful. I unfortunately have this issue in a furnished basement with no access. Does anyone have any tips for this situation that don't entail tearing out a finished ceiling? appreciate your responses.


 with the duct work sheet metal I had these issues as well. opening up the covering is needed to see whats going on..

what I did was this . dropped all the main duct work. removed all the nails used to secure the duct work to the beams ,, then used screws. used sealant to connect all the duct work together. wrap the duct work with the aluminum foil plastic bubble insulation .. used aluminum metal tape to secure this insulation. each section screwed in the the beams.

the round pipes I sealed at the connection to the rectangular duct work using metal tape and then sealant. wrapped the round duct with the same insulation and taped.

with this secured to the structure , insulated, sealed I have more heat in the upstairs living area , less dust because it is all sealed , gas furnace vent gases do not get into the air ducts ..this is now very efficient..

I have much more air flow and the system heats up the house much faster ..

not even a pop since this was done ...it cannot more ... 

if you do not remove the covering over the ducts [sheet rock/plaster ] this will not be repaired.. I have saved much on my gas bill since this work was done...less dust !


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