Water Heater Flue Pipe Making Knocking Sounds

[Ganq]

Hi Everyone,

We are in a 2 year old house. Every time the water heater turns on we hear loud knockings sound in the attic. We were able to find the pipe causing it - It's the flue pipe coming out of the water heater on the 1st floor and going up to the attic and having the exhaust out. The pipe is definitely expanding or cooling which is fine but it makes loud banging sounds every time it expands or cool. Surprisingly it's not happening in any of the near by homes built by the same builder/plumbing company.

Any idea what could be causing this and how to mitigate the loud banging noise - It's loud enough to wake us up in the middle of the night. Wasn't able to upload the videos directly here so please see the link for the 2 videos: First one is from our bedroom where the loud knocking sounds can be heard and the second one is from the attic showing the flue pipe creaking - Can feel the vibration on the flue pipe when we touch it.

https://imgur.com/a/V5r8Yuz

Any help would be greatly appreciated. Been working with the original plumbing company for almost 2 years now and they haven't been able to figure it our or give us an explanation for why it only happens in our house and not in any of the other neighbors.

Thank you!

 

[Fitter30]

Pull that insulation back how tight is that hole to pipe and at the first floor?

 

[Sponsor]

 

[Ganq]

Pull that insulation back how tight is that hole to pipe and at the first floor?

Thanks for the response. The plumbing company had cut the drywall in many different places along the pipe route and have tried to free it from any tight spaces/clamps that could be constricting the pipe from expanding. Per their request we have also removed a lot of the insulation from the attic so that it helps them investigate. But so far they haven't been able to pinpoint what could be causing these knocking sounds. Any idea what could be the source for this? could something be wrong with the heater itself?

At this point even if we cannot get rid of the noise completely we are okay with that as long as we can reduce the intensity of the knocking sounds so that it doesn't wake us up in the middle of the night - That would be great.

Thanks again!

 

[Fitter30]

Take a pic of the heater and flue pipe

 

[Ganq]

Take a pic of the heater and flue pipe

Please see picture of water heater and the flue pipe pointed by the yellow arrow. The flue pipe starts thinner but if you look towards the top of the picture, its diameter increases and that's what we see in the attic as well. Thank you!

 

[Ganq]

Take a pic of the heater and flue pipe

Is there any kind of padding or dampers (Not sure if there is such a thing) I can use around the pipe/clamps to reduce the knocking sounds. Pic attached in the previous post. Thank you!

 

[Jeff H Young]

Hadn't dawned on mne the vent was plastic, sheet metal vents can be noisy especially oval type b.
the plastic I think is tightly strapped to wood. with that type of vent ,insulation doesn't need to be away. to really fix it a single small hole might not cut it .
its expansion and contraction heat and cold that causes it.
you gotta crack eggs to make an omlette! in other words open it up and fix it these guys are pros replace entire vent system if you have to? I'm pretty sure its clamped really tight somewhere and moving when it heats up. unfortunately an expensive repair dry wall paint and patching costs.

 

[Fitter30]

The clamp used in the attic can't see that making noise the way it's made. That ell in the attic is that sitting on the board? If it is push up on that top 45° by the heater see if the pipe moves. Even a 1/4" could put a piece of carpet between board and ell in attic.

 

[Jeff H Young]

Noise is coming somewhere . Either you are overly complaining or they need to step up, or bring another contractor out and replace entire vent and strap with care. plastic pipe is expensive but it isn't gold. The entire vent is totally accessible no pipe chases etc that's the attic ? A single story?

 

[Jeff H Young]

never mind its a 2 story. well obviously they arent busting open walls they just look shrug shoulders and leave

 

[Ganq]

@Fitter30 - Thanks for the response. Not exactly sure I understand “If it is push up on that top 45° by the heater see if the pipe moves. Even a 1/4" could put a piece of carpet between board and ell in attic.”

I did ask the plumbing company if they could remove some of the clamps in the attic and they said that the pipe needs to be slanted so that any water in the flue flows back down so they need to keep the clamps the way it is.

Another thing they mentioned is that because of regulations folks put some kind of fire retardant foam or something around the pipes through walls to seal shut - That could be a problem. But they have already made a few holes in the dry wall and have tried shaking/wiggling the pipe loose. Not sure where else it could be stuck.

I did notice last night when the knocking sound was happening, you don’t feel any vibrations/jittering in the flue pipe at any of the holes they have made in the dry wall. However, you can feel the vibration in the attic from where the sound is coming from as shown in the picture in the main post.

What kind of padding should I be using to dampen the creaking/knocking sounds.

 

[Ganq]

@Jeff H Young - Hi, thanks for the response.

Unfortunately we are stuck with this Plumbing company ‘cause they were the ones who did the work originally with the builder and technically we are still under warranty and the builder is coordinating with the plumbing company for this repair. But lately none of them are responding to our requests and have kinda left us in the dark. Not sure what else to do.

May be get an inspector or complain to city - Not even sure if that’s the right way to go.

Yeah, it wakes us up and our guests in the middle of the night so we aren’t overly complaining. The sound is almost like someone using a hammer.

 

[Jeff H Young]

The builder can often pressure the plumbing sub as it reflects on the builder assuming you bought the house from a builder and had no contract with plumber. often though a bad subcontractor leaves the builder holding the bag In California if the plumber flakes out the builder is still responsible.
It can come down to a civil matter if they refuse to fix it and you are forced to hire it out then you have reason to sue for costs. doesn't mean you automatically win but you do have recourse. The government meaning city county , or state licensing etc. or bonds might be able to help. but at a certain time . 2 years is long to not have it resolved ask builder what they propose to satisfy you once and for all? polite and civil but where is this going ask them. I think they are hoping you give up

 

[Ganq]

The builder can often pressure the plumbing sub as it reflects on the builder assuming you bought the house from a builder and had no contract with plumber. often though a bad subcontractor leaves the builder holding the bag In California if the plumber flakes out the builder is still responceable.
It can come down to a civil matter if they refuse to fix it and you are forced to hire it out then you have reason to sue for costs. dosent mean you automaticaly win but you do have recource. The government meaning city county , or state licensing etc. or bonds might be able to help. but at a certain time . 2 years is long to not have it resolved ask builder what they propose to satisfy you once and for all? polite and civil but where is this going ask them. I think they are hoping you give up

Thanks for the response. I did reach out to the builder and currently waiting for a response back. The plumbing company is still working with the builder on new projects nearby and elsewhere - We see their vans all over.

We aren’t exactly allowed to go to the plumbing company directly and have to go through the builder contact. I am in Illinois, what would be a proper course of action in case we don’t get any help from the builder/plumbing company:

1. Should we hire an inspector?

2. Complain to the city/county?

Or do we have to get a lawyer for all these?

Please advise. Thanks again.

 

[Jeff H Young]

I can' tell you for sure But I feel the builder is responsible to you he can even hire a different plumber but he must warranty the work. All correspondence is in your interest to be documented, Texting and emailing is better than verbal but both is good.
I hope you have correspondence that shows the builder acknowledging an ongoing problem that they agree to repair?
hire an inspector you will pay an inspector your choice.
sure you can go to government like the city building department and if you are lucky they can steer you where to take your issue. I cant I'm imagine that would be the right place but they could very well suggest next step.
But you came on here looking for advice to fix it and You have someone the builder that has agreed to fix it so why not just turn the heat up? do yourself a favor document every call and visit to your house and follow up with email or something.
I think they might be a little shy on opening up thge drywall making a mess.
how many times in 2 years have you had them come out 3 times 12 times? when ever the fix doesn't work don't wait call next day

 

[Breplum]

City/county are not going to be any help.
I doubt an outside inspector will have anything to contribute. Even the WH mfr customer service # might have something to contribute. That noise is way-extreme if it is just expansion/contraction.

Unfortunately, if the builder does not respond reasonably, first, a complaint to Contractor's license board if you have such. And an attorney, though, frankly, an attorney's retainer alone may cost more than a complete replacement with either another brand of forced draft or go to a condensing tankless with plastic venting. My favorite, Navien 240A2 series can travel 60' in 2" PVC, or tie in to the existing at the 2" or the 3"

 

[Jeff H Young]

The builders at least many or some do care about reputation especially if its an unavoidable obvious defect.. Only thing I think is a city or government employee might direct you in right direction. uIm not sure contractors board responds to a noise issue. but I've fixed things before for companies I worked for and we felt obliged to fix especially when its obvious our fault.

 

[GrumpyPlumber]

While I know at least one member above is sure the city won't help, I might suggest calling the plumbing inspector and asking - this is a gas vent, CO hazard, state code enforcement takes CO danger seriously.

That said, if the knocking happens for a period and then stops with the heater still running, it's thermal expansion - if it's constant, then it's probably not secured, may need seismic/perpendicular restraint in the attic, if it's on long hangers it could be swinging (literally) via vibration from the power-vent blower.

 

[Jeff H Young]

Talking to anyone could help even one of our advice could help. What I think he should do is continue to try to get the builder out there , picking city's brain might help , I think you might get better advice out of them than actual action like having him condemn or red tag your water heater. also I'm not suspicious of a CO leak

 

[Ganq]

I can' tell you for sure But I feel the builder is responsible to you he can even hire a different plumber but he must warranty the work. All correspondence is in your interest to be documented, Texting and emailing is better than verbal but both is good.
I hope you have correspondence that shows the builder acknowledging an ongoing problem that they agree to repair?
hire an inspector you will pay an inspector your choice.
sure you can go to government like the city building department and if you are lucky they can steer you where to take your issue. I cant I'm imagine that would be the right place but they could very well suggest next step.
But you came on here looking for advice to fix it and You have someone the builder that has agreed to fix it so why not just turn the heat up? do yourself a favor document every call and visit to your house and follow up with email or something.
I think they might be a little shy on opening up thge drywall making a mess.
how many times in 2 years have you had them come out 3 times 12 times? when ever the fix doesn't work don't wait call next day

Yes, we do have quite a bit of email communication over the last 2 years about the knocking issues. I don't exactly recall what all the emails say but there is definitely an acknowledgement on the builders part that a problem exist and this kind of loud knocking isn't normal - I have email/text messages from the builder rep + the construction manager saying this isn't normal knocking sounds a pipe should be making over text.

In the last 2 years the plumbers have been here for atleast 7-8 times for this particular issue.

I did hear back from builder and it seems the plumbing company is asking them to replace the water heater and see if that fixes it. The builder is okay with that but they did ask the company if that will that fix the issue? and the plumbing company isn't sure so we are kind of in a limbo right now.