For quiet some time I saw some treads here and there where people were trying to bypass my site and find a solution online some place else. But this one below had really raised my eyebrows, not to mention its so funny!

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

We just moved into our house two weeks ago. Just about every night I wake up to, what I would call, clicking or popping of the duct work under our bedroom as the ducts heat up at the start of a cycle and for several minutes after the furnace quits. I've heard it in houses before but never this loudly, or for this long a time period. The basement is unfinished so I have complete access, and these 2 ducts are the furthest from the furnace (60' run).
Any words of wisdom on how to reduce, dull, or eliminate the metal noise? It is driving me nuts! Thanks all!

What this poster is describing is actually a ticking noise. But if he wanted to get “any words of wisdom” – he is definitely in the wrong place!

Answer 1
Definitely 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 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
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.

So, what this guy is suggesting is to put duct on legs and see what happens… And if it do not help make some dents in the duct! But see below there is even better and much bolder solution!

Answer 2
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.

Let me start with the notion that it would never work and I doubt that he even ever tried to do it himself anyway – just his wild thoughts…

Answer 3
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.
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.

What this so-called pro trying to suggest is a fix to the different problem! I would assume that at this point he already forgot what the original poster was asking for!

Answer 4

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??? DA...'EY, YURI, WHEN DO I GETS TO SMASH 'D DUCK' ALREADY???
He does the tear outs between wrestling dates!

At this point the party gets wild! Now they have started to make a fun!
So, I thought that that poor fellow got enough and I was stupid enough to offer him my help. I’ve sent him an email:

Hi, you can go to my site and find a solution there, or you can hire me, because I'm your neighbor, and I'll fix it for you.
Ed

But this guy didn’t even look in my profile, probably because he still has a dream… dream of free, and ultimate solution!

Follow up
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, it’s 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.

Question

Hopefully this is the right sub forum to ask but is it OK to lay PVC (plumbing vent, HVAC) on top of a 2x4 or lumber for support? I noticed one of the 2x4 is slightly loose and made sure none of the PVC is held tightly around plastic J straps.
As you can see from the picture this is in my attic where temperature swing can be drastic. I am hearing intermittent popping noises that I am thinking could be PVC movement.
What's the best practice to support PVC? Would it be better for me to hang the top using rubber straps?
I also noticed intake and exhaust PVC from my HVAC equipment surrounded by spray foam and I am curious if that would restrict movement and cause noise?

Answer

I would leave them alone. The popping noises are pretty hard to get rid of.
My attic can be -40F in the winter and when I dump hot water down the sink the vent gets a load of steam and can pop. Just normal thermal expansion.
Leave the furnace venting alone as you have a concentric exhaust kit and both of the pipes need to be loose as they expand/contract at different rates and will make lots of noise if tight. As long as they are not sagging and have dips in them/low spots where water can collect they are OK.

“The popping noises are pretty hard to get rid of” – this guy is wrong…

Follow up

Hi Yuri... thanks for your response. I am with you on this... I can totally see myself screwing things up more.
I checked pipes and they seemed loose enough to move. I am concerned with the 2x4 being slightly loose so I might tighten that a bit.
Finally, I have a separate furnace room in the attic with full insulation. That's where the HVAC pipes (exit). These are surrounded by drywall and spray foam so they must be pretty tight. Could these make noises? I don't want a gap around the pipes since furnace room is conditioned room.

The OP say: “I checked pipes and they seemed loose enough to move”, but he doesn’t realize that it contradicts Yuri’s suggestion – the pipes are loose, but still making noise!  

Answer

They usually make noises right where the concentric kit is (part where they join at the roof). I doubt you can hear that. The noise is there because you have a hot pipe and cold pipe attaching at the same spot and they expand at different rates. Not actually hot but warm.

If it ain't broke don't go fixing it is my motto.
There is not that much expansion either. Unlike a steam line which can move a lot. Sometimes the noise is if it is tight against a furnace or ductwork and then people can hear it.

“They usually make noises right where the concentric kit is (part where they join at the roof).” – total BS! This guy knows nothing. In my house I have two concentric kits and none of them making any noises.

• How to find a source of the ticking noise in your basement, wall, B-vent pipe chase or in the attic and how to quiet it down once and for all
• How to cut a drywall if the source of the noise is behind it and how to fix drywall when it is done
• What to do if the ticking noise is coming from the wall and how to eliminate it without cutting a drywall
• What to do if your ductwork is making ticking noise in the attic
• How to eliminate a ticking noise if it is coming from PVC or copper pipes of your water heater or boiler inside and/or PVC concentric cap outside of your house