Hot Topics: Boiler Making Gurgling Noises

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Original Post: Boiler Making Gurgling Noises

JRivera - Member

1983 Peerless Series 85 Gas Fired Boiler

Model: 85-140-WPC-H

This boiler serves three zones of baseboard radiation in my house with Honeywell zone valves and a single Taco circulating pump. One zone is upstairs and the other two are on the main floor. The boiler sits in the garage at the same elevation as the main floor.

My issue is that the boiler makes gurgling noises when it fires, almost as if it were boiling water and bubbles were forming. My neighbor has the same boiler and similar setup and his hardly makes a noise. The only difference is that my system has been filled with water and he thinks his was filled with a glycol solution the last time it was serviced.

I have been doing repairs on this system myself now for several years including replacement of valves, expansion tank, and recently the aquastat controller and air vent. It seems I have drained and filled this system once a year now for several seasons. When I fill the system, I make sure to place the discharge hose in a bucket so that I can watch until the bubbles clear as I cycle through each zone until I am certain that I have bled all the air out of the system. I am probably overly cautious in my attempts to try and eliminate the noise.

I have the aquastat set so that the boiler is operating in the range of 170 - 200 degF. The pressure gauge reads 25 psi. I cannot imagine that the noise is coming from boiling of the water as the noise begins almost immediately from a cold start. I recently replace the Taco air vent with a Honeywell EA122 because the Taco vents typically leak and I wanted to try something different and make sure the air vent wasn't the problem. The problem still exists. I am at a loss. Any ideas?

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NJT - Member

"It seems I have drained and filled this system once a year now for several seasons."

May be part of the problem... maybe not.

Are the sounds you are hearing confined to the boiler itself?

I mean, you would know if it was air in the system because you would hear the bubbles running through the zones and such, right?

If you say it sounds like boiling, it might be what some folks call 'kettling', like when ya got a big pot of tomato gravy simmering on the stove... and BLUP! BLUP! you get those little 'volcanoes' on the top.

This can happen when you have sediment in the bottom of the boiler that causes hot spots and yes, sort of a localized boiling.

It can also occur if the flow is not adequate in the boiler. Are you sure your pumps are working properly?

With frequent emptying and refilling of a boiler, there can be excess sediment accumulating in the boiler from all the fresh water that is being put in.

So, is it confined to the boiler? or do you think it's air in the system?

Do NOT TRUST THAT BOILER GAUGE! They are lying evil devices put on this planet to confuse and confound us!


JRivera - Thread Starter

The sounds are definitely confined to the boiler itself. I have never heard bubbles traveling through the pipes or baseboards. I replaced a dead Gundfos pump several years ago with an equivalent Taco cartridge circulator (Model 007-F5, 1/25 HP) and have never had a problem with the system working to heat the house. I am almost certain that the pump is functioning properly but I don't have a means to measure the flow rate.

The pipes are all copper throughout the house. Each time I have drained and filled the system, I definitely get very fine particles (smaller than grains of salt) coming out of the system. They are dark in color and I have just assumed that it is corrosion coming from the boiler. When I drain and fill the system, I always lift the lever on my pressure regulating valve to make sure I am getting full flow through the valve and have made sure the water was running clear and without bubbles before completing the fill.

Could some of the sediment still be left in the boiler and is there a way to address this?

The boiler is nearly 30 years old, could it be that portions of the boiler have corroded to the point that these localized hot spots are permanently there?

Should I be saving my money expecting this boiler to begin leaking sometime soon and in need of replacement?

The gurgling noises seem to have been getting worse in the last several years. The last time that I paid a contractor to work on the system (probably 7 years ago), I watched him refilling the system and asked about corrosion inhibitors. He stated that they sometimes put glycol in the systems but that it wasn't really necessary. Plain water was fine. What is your opinion? Could that have been the start of this issue? I don't remember the noises occurring at that time.

Thanks for your help.

gilmorrie - Member

Routine draining and refilling is not necessary or recommended - because it introduces air and promotes corrosion. The water from a circulating system with steel or iron components will always be brown in color, which is normal and not a problem. Corrosion inhibitors are not required if you have air elimination device that is working - that would be something to check and probably replace.

You say that the pressure is 25 psi. It's either a bit too high or the gauge is wrong, reading high. High pressure shouln't cause gurgling, but low pressure could. 200 deg is too high.

Do you hear the gurgling with the pump running but the burner off? Sometimes, a boiler will rumble (not gurgle) due to instability of the flame. An experienced boiler serviceman could help pinpoint the source of the noise. Or you can make a video, with sound, and post it here.

NJT - Member

"Could some of the sediment still be left in the boiler and is there a way to address this?"

IF the problem IS 'kettling', then yes, there is sediment in the bottom of the boiler. As for a method to flush it out... can't really help ya there. Maybe Mr. Grady White will come by to offer some suggestions... or... anyone?

I like Doug's idea of a vid with audio... we might be able to tell more if we could hear it.

"Should I be saving my money expecting this boiler to begin leaking sometime soon and in need of replacement?"

Always a good idea to have some gold coins in the mattress... but this probably isn't a sign of imminent doom. Still... 25 years is a good run for a boiler of that vintage, but it's not unheard of for them to last much longer. Usually the reason they get replaced (if not leaking) is to try for higher energy efficiency (and that often takes ten years or more to see a return on!).

Please verify your gauge. You don't know what you're dealing with until you have an accurate idea of what the pressure in the system really is.

JRivera - Thread Starter

The gurgling noise only occurs when the boiler is firing. I never hear the noise when the pump is only running. I haven't had time to get a gauge but I'll get around to that, maybe tomorrow. In the meantime, I took a short video with my smart phone and even managed to convert it to a .wmv file so that it could be played with Windows Media Player. Problem is that I think the file is too large to post at approximately 3 MB.

I can dumb it down some and zip the file but it still exceeds the 50 kB max file size for attachments. Am I missing something? I could send you a file via e-mail or post to my Google docs site but you would have to contact me via e-mail. NJ Trooper appears to be a moderator, so maybe you can contact me or give me direction on how to get the video to you?

gilmorrie - Member

I failed to ask one other question: does the noise occur with the burner firing and pump not running? And does the noise occur when the boiler is either hot or cold, and the burner initially fires?

I think there are free? websites where you can post big attachments and then allow others to download them.

gilmorrie - Member

Google "upload large attachments free"

It would be best to post your wave file where anybody here can get to them.

JRivera - Thread Starter

Got a gauge, though it is scaled 0 - 100 psi. Boiler starts cold at 20 psi. Aquastat shuts the burner down somewhere around 190 - 200 degF and allows it to start again somewhere around 160 - 170 degF. I am measuring the temperature of supply piping as it exits the boiler with an infrared gun about an inch away from the pipe. The aquastat controller is a Honeywell L8148E which is supposed to have a fixed differential of 15 degF, but I must have one that came from the factory fixed a little closer to 30 degF. The pressure rises to about 24 psi when the temperature reaches the shutoff temperature.

I disconnected one of the wires from the circulating pump so I could fire the boiler without the pump running. I get the gurgling noises regardless of whether or not the pump is running when the boiler is firing. I never get the noise with just the pump running. The noise starts within about a minute after the burner fires, regardless of whether it is a cold start or if the boiler is firing again because the aquastat has again reached the low end of its differential.

It does sound like water boiling and I'm guessing NJ Trooper is correct that it might be "Kettling".

With regard to the pressure, the system has a Watts feed water pressure regulator that says on the tag "Set 12-15 / Range 10-25". I checked the city pressure at one of my hose bibs and the gauge reads close to 40 psi. I have never worked on this regulator but have some literature that says there is a strainer screen that should be serviced twice a year. Are my boiler system pressures OK? Should I attempt to change the pressure setting or clean the screen? Would this have any affect on the noise issue?

I had my 13 year old help me post the video to YouTube. Here's the link. Note that the predominant noise you hear is the gas valve hissing. The gurgling is in the background.

Boiler Gurgling Noises - YouTube

gilmorrie - Member

Sounds like popping, sort of like a percolator coffee pot. I can't place it - and don't know what to suggest. Maybe others will think of something.

JRivera - Thread Starter

Never heard back from NJ trooper after I posted the video complete with sound byte. I actually woke up yesterday to a strange noise in my baseboard radiator at the far end of the house. Not bubbles moving through the lines but the noise at the boiler being transmitted through the pipes. I'm hoping someone views the video, hears the noise and can tell me what I might be able to do to make it go away. The noise has definitely increased each year over the last several years. Any thoughts would be appreciated. Thanks.

gilmorrie - Member

As Trooper suggested, the noise is likely kettling - but I think it is likely that it is due to lime buildup on the water side of the heating surfaces. Is your city water's hardness high?

That would point to calcium carbonate dissolved in the water. The solubility of carbonate is much lower when the water is heated. When you drain and refill the system, and start it up, the carbonate plates out on the hotest part of the boiler. Eventually, the carbonate concentration in the water drops to equilibrium, until you drain and refill the boiler. Then it starts all over again.

You can Google for products that are supposed to remove the lime buildup. I'm skeptical myself.

NJT - Member

All I can really do is repeat something I said in an earlier post:

"IF the problem IS 'kettling', then yes, there is sediment in the bottom of the boiler. As for a method to flush it out... can't really help ya there."

I don't have a solution for your problem, sorry.

I guess all we can do is wait and see if anyone with experience with this problem can offer any suggestions.

gilmorrie - Member

If, as I tend to think, the noise problem is lime buildup on the water-side of the heat transfer surfaces, I would live with it until next spring before trying any of the chemical potions sold for limescale removal. Then, you will have time to possibly replace the boiler if the treatment goes bad.

If or when you replace the boiler, and assuming you do have hard water, here are some suggestions: don't drain and refill the system, unless there is a good reason why it has to be done; and install a water softener ahead of the boiler fill valve.

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