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  1. #1

    Tea-kettle whistling noise: Do I need a flush or an entire new unit?

    Hi there:

    I’m hoping for some help on the following series of problems I’ve been having. I am NOT looking for a DIY fix, but need some guidance on which professional option to choose here.

    1) I have a Utica gas boiler, forced hot water with two zones. It’s at least ten years old, and was in the house when I bought it.

    2) Three weeks ago I had the gas valve replaced. The valve had been buzzing at startup and the boiler would cycle on and off intermittently. When it was tested by the technician, the gas pressure was low.

    3) The unit worked fine for several days, then the intermittent on/off cycling returned. I tried to wait to call back the repairman until I could reproduce the problem. Before I could reproduce it reliably, the pilot light stopped staying lit.

    4) Long story short, the technician returned. After several minutes, he sheepishly admitted that he had not properly tightened the new thermocouple when he did the gas valve replacement. The boiler (which had been off for over a day) fired right back up, and we were both satisfied that both zones were getting heat.

    5) About 20 minutes after the tech left, and once the boiler heated up to working temperature, a tea-kettle whistling noise began to come from inside the boiler unit. This noise had never appeared before, and it now occurs each and every time the boiler fires—but only when the gas jets are firing. It does NOT occur only when the circulating pumps are active, and there is no leak, no evidence of steam escaping, and no loss of pressure (steady at about 20psi). It takes a minute or two for the whistling to start (seems temperature dependent)), and sounds almost as if there is a now pin-sized hole allowing air to be forced through somewhere within the block. When the unit fires down, the pressurized noise also dies down and goes away. This noise never occurred before the technician’s visit to fix the thermocouple.

    6) The tech returned today and was stumped. Re-tested for gas pressure, circulating pressure, and operating temperature—all are fine. He removed the side and back jacket panels and looked internally at the unit with a hand mirror, and could see no leaks. According to his diagnostics, the unit runs at 78 percent efficiency.

    7) After consulting with his boss via phone, the tech offered me two options. The first was to try and “skim” the system with a chemical flush. He said it was coincidental that the unit just started making this noise right after his last visit, and that a sludge buildup might be causing a blockage, and thus the noise. He said it was a 50/50 shot at making the noise go away, and offered go guarantee on the work.

    8) The second option was to replace the boiler with an entire new unit. The tech offered me several pricing options, and although I don’t doubt that this unit is old, I think it is a radical step to spend a lot of money on an entire new unit without knowing the cause of the current problem. I was also a bit scared away by his hard sell—i.e. “If you commit to buying a new boiler from us TODAY, we’ll refund the cost of the work you’ve already had performed, but you must make this decision TODAY to get the refund.”

    Right now I’m leaning toward getting a second opinion, but would appreciate any feedback to help me make my decision.

    Thanks in advance for your help,


  2. #2
    Join Date
    May 2002

    I hate

    strong arm tactics in selling.You must buy today eg. The tea kettle sound may be the circulator or the venturi . I would call in another company

  3. #3
    Join Date
    Sep 2005
    Bay Area, CA
    I would like to know what the problem is before taking action. What if the whistling came from a design issue with the home causing the system to break down prematurely? Replace it and it'll just happen again in 10 years.
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  4. #4
    Join Date
    May 2002

    Only way

    to know is to find someone who can troubleshoot . I've never seen boiler piping clogged , to the point that it made noise. Did they check gas pressure or listen to the curc.

  5. #5
    Yes, the gent checked the gas pressure and the circulation pumps.

    The part I don't understand about the recommendation of the chemical flush is that the issue doesn't seem related to the H2O circulation.

    When the flames inside the boiler shut off, the noise slowly winds down within 10 seconds. Even with the circulation pumps still running, there is no noise--it is directly related to the boiler being fired up.

    There is heat to all zones and no other noitceable performance issue. Pressure is steady at 20 PSI (up to 25 when hot). And the temp. on the aquastat is within its usual range.

    It's just that the noise itself is so damn annyoing...

  6. #6
    Join Date
    May 2002

    It really

    sounds like a gas valve or pressure problem

  7. #7
    I should clarify: The whistling/whooshing sound only occurs when the boiler flames are firing AND once the internal temperature of the boiler has reached its peak operating temperature.

    This happens after about 10 minutes when it's firing up from dead cold, or within a minute after firiing if the unit has already been hot.

    The whistling slowly builds into a rhythmic whoosing sond that remains constant. When the boiler fires down, the process reverses, and the whooshing dies down into a slow whistle before it stops.

  8. #8
    Join Date
    Mar 2005
    Suppy NC
    could be a build up on the HX causing impingement or hot spot
    cleaning the HX may help

    could be not proper draft thus same as above

    time for a second opinion. Flushing the water may cause more problems and not fix the one you have

  9. #9
    Thanks...Good point on the HX suggestion. That sounds exactly where the whistling is coming from.

    I will be calling another company to get a different opinion.

    What kills me, though, is the "coincidence factor."

    Remember, the first time this occurred was 20 minutes after the tech stepped out the door. (He had replaced the gas valve two weeks ago, but when I complained that the pilot light would not stay lit, the gent returned. He then rather sheepishly admitted he had forgotten to tighten the thermocouple correctly.)

    What could tightening a thermocouple do to change the dynamics of the way a gas boiler sounds when firing?

    I thought it might have been something stupid--like the gas burner tubes weren't re-seated correctly or that he had left an inspection port ajar.

    Could what he "changed" be that by tightening the thermocouple, the boiler now fires up at its optimal temperature, exposing a flaw that was not there when the boiler was working inefficiently?

  10. #10
    Join Date
    Mar 2001
    Remember, he said the gas pressure was low.. where did he set it to? Perhaps this problem happened before, & someone reduced the gas pressure to compensate (perhaps flow rate thru boiler is too low) Now there is enough heat to start the water to change to steam @ full fire & full temperature.

  11. #11
    Join Date
    Dec 2008
    Buffalo NY


    Quote Originally Posted by Moose View Post
    Remember, he said the gas pressure was low.. where did he set it to? Perhaps this problem happened before, & someone reduced the gas pressure to compensate (perhaps flow rate thru boiler is too low) Now there is enough heat to start the water to change to steam @ full fire & full temperature.
    That is exactly what I was thinking when reading the OP post. Could have just enough output to change to steam. Temp gauge may be off. Also you could have a problem with temp limit. Get a different company in there to check this out. Steam in a hot water boiler is not good.
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