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Loud Bangs from Weil McLain Boiler - Steam Heat System

Ritzy Member Posts: 34
In 2001, I had a new Weil McClain (45) Gas boiler replace an

old Weil McClain Gas boiler (75).  The plumber told me that the old boiler

was too big for my house (1200 sq. ft.); however, the new gas boiler did not

provide the same kind of even, comfortable heat that the old gas boiler


Be that as it may, after about 5 yrs. (in about 2005-2006), this new gas boiler

began to began to BANG LOUDLY for 3-5 minutes as it started-up.   Although

the steam pipes throughout the house have made banging sounds themselves,

intermittently, we realized that the radiators should be elevated on one side

(with a piece of wood) to reduce this water hammer.  We took care of that

problem years ago.

Presently, the LOUD BANGING sounds from the

boiler itself come from the back of the boiler that faces the chimney

wall.  These LOUD BANGING sounds give

the impression that the boiler is about to explode....visitors to my house

(and, my family) have been terrified by these sounds.  These LOUD

BANGING sounds occur just after the pilot light kicks-on the ignition...just as

the boiler begins to operate.  The LOUD

BANGING sounds continue for about 3-5 minutes as the boiler warms up.  Two

plumbers have looked at the boiler and could not determine what is causing

these loud banging sounds.  

I have taken a bucket of water from the boiler once every 2-3 weeks

throughout each heating season and replaced it from the water feed.  The

glass tube is clear and is kept, always, at about 1/2 full level.

Literally, these loud banging sounds, originating from the boiler itself, scare

me tremendously.  Anyone have any suggestions to correct this

problem?  I have attached a picture of the boiler.


  • Paul Fredricks_3
    Paul Fredricks_3 Member Posts: 1,557

    I don't have a lot of experience with this, but it sounds like there may be a buildup of mud or sediment in the back of the boiler. the only way to know is drain it down and flush it out with a wand.

    Others here would know better than me.
  • Brad White
    Brad White Member Posts: 2,398
    edited March 2011
    I would check to see if

    the returns are clogged and how clean the boiler is, inside. What leads me to this is that the problem started relatively recently and degraded to this, rather than on Day-One.

    If the return to the boiler is lessened or the boiler has a lot of rust in the bottom, that uneven heating can trigger hammering, with trapped water below the crud and against the boiler wall opposite the flame, hitting the boiling point.

    Normally, but not always, the kind of banging I describe happens once the system is warmed up, but in your case it is on start-up yet it is inside the boiler, so I suspect sediment.  -Edit: Mud as Paul said.

    What is the condition of the water you remove and do you get any solids out? Have you used any cleaning products in the boiler, such as Squick?
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"

    -Ernie White, my Dad
  • Ritzy
    Ritzy Member Posts: 34
    Thanks so much!

    Thank you for the suggestion.  I appreciate it.  I have tried to keep the boiler clean by emptying a bucket every 2-3 weeks; however, maybe, that was not enough to keep sediment forming in this boiler.  I never had this problem with the prior Weil McClain.
  • Ritzy
    Ritzy Member Posts: 34
    Clear Tube Water

    I have never used any cleaning products in the boiler at all.  The water that comes out, when I take a bucket off of it, generally is 1/2 rusty.  It is never clean...although the tube water is crystal clear.
  • Brad White
    Brad White Member Posts: 2,398
    It may not be the boiler

    but a collection from your piping coming back to the boiler. It is a "system" after all! So while you are rodding out your boiler, check your returns. Hopefully there is a plug or valve at the end on a tee. 
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"

    -Ernie White, my Dad
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,322
    I think the fittings for the sight glass

    are clogged at least at the lower fitting. When I see crystal clear water in a 5 year old steamer I get suspicious. You may be over filling the boiler and not know it. with the boiler cold and shut off you or your plumber need to see if the lower fitting is clogged. I do this by removing the lower valve stem and inserting a small wire or length of solder through the valve body. HAVE A BUCKET HANDY!. if it is clogged you will get a few dribbles when you remove the steam and a whole bunch after you poke the wire through. This is also a good time to clean or replace your pigtail.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • Ritzy
    Ritzy Member Posts: 34
    Pigtail has been changed

    The system has never been fully emptied since installation; however, the pigtail has been changed.  Someone mentioned a Hartford loop problem once...then another plumber I had examine the boiler said that the loop was ok. 
  • gerry gill
    gerry gill Member Posts: 3,078
    I agree with Paul.

    sounds like you may need to wash out the boiler..hopefully the installer left a way to do it..
    Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

    RDSTEAM Member Posts: 134
    what do you guys think about

    the loop? i know it wouldnt cause any banging at the start of the cycle but with the nipple being a pretty decent size, it might cause some problems during the cycle. why did he downsize the boiler?? did he check the edr of the house to come to his conclusion??

    p.s insulate those pipes!!!
  • Ritzy
    Ritzy Member Posts: 34
    Claimed that Prior Boiler Was Oversized

    I just want you all to know that I appreciate all of your suggestions and must shout out a grateful, "Thank you!" for all your input.  The fellow who mentioned the Hartford loop suggested that maybe my boiler's "loop" was not set at a proper distance and may be involved in my boiler's noise. 

    Some overhead pipes in the basement...a short distance from the boiler...have silver, vertical vents on them that have never been removed, cleaned, or changed.  Might changing those vents help the situation?
  • Brad White
    Brad White Member Posts: 2,398

    I think what you are describing are main vents.  Usually these are located near the ends of the steam mains and their purpose is to remove as much of the bulk air ahead of the steam with each steam cycle.

    Without good main vents, that job falls to the smaller, lower-capacity radiator vents and your house will have more hissing than a Joan Rivers concert.

    There is not a direct correlation with banging that I can see, regarding vents, maybe an indirect one in that they will not relieve vacuum when steam condenses. (A sudden vacuum creates a different kind of banging, nothing as violent as you describe.
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"

    -Ernie White, my Dad
  • Ritzy
    Ritzy Member Posts: 34
    Truly Violent Banging

    Yes, Brad, this is truly violent banging.  If I could afford it, I would change the boiler...if that would help the situation.  That's how scary the banging is.  I could see my replacing the boiler and the banging still happening if there is a problem with the pipes & venting themselves.  Does flushing out the system with a chemical hurt the boiler and/or system in any way?  My mother mentioned that her boiler was purged once that way...and she didn't have any banging noises from it beforehand like my boiler emits.  Her boiler is the same exact model as my Weil McClain Gas boiler (45).  Thank you, again!
    RDSTEAM Member Posts: 134
    try some tsp or mex

    these will help flush out your system but you will need to install a shut off valve on your return right by the union. change the boiler drain on the return to a full port ball valve and just follow DH instructions on system flushing. if you need them i will be glad to type them up for you.
  • Ritzy
    Ritzy Member Posts: 34
    Need instructions

    Thank you, RD.  I would appreciate the DH instructions for flushing...if possible.
  • Rod
    Rod Posts: 2,067

    Hi- Here's a link to a some tips on flushing than Dan (DH) put together.


    Sometimes it is easier to just replace the wet return with new pipe. Copper is okay for this as the wet return is a non steam pipe and copper has an advantage in that it is less likely to corrode than black iron.

    - Rod
  • Ritzy
    Ritzy Member Posts: 34
    Thank you

    Again, thank you for your suggestions.
  • pcmeiners
    pcmeiners Member Posts: 1
    edited February 2013
    Boiler noise, check the pipe hanger tension

    Installed a peg 40 steam boiler, loud pinging noise from the boiler

    started after a week during heat and cool down, roughly every 30 seconds

    for minutes, loud enough to heard through the pipes on the second

    floor, making it hard to sleep. Followed multiple post here and

    elsewhere as to flushing the system which did not alleviate the issue,

    I had already adjusted the pipe hangers before installing the boiler, so no added weight was applied to the boiler during the install; the adjustment  was made a week prior to the install. Turns out I had to lift the pipe manifolds via the pipe hangers again to remove any downward weight applied by the piping, after the install; I was careful with the pipe fitting, so the install did not cause the issue .

     Luckily I leaned on one of the hangers finding it  with less tension  as

    compared to the initial adjustment . Basically I lifted the manifold to

    the point of just lifting the boiler a tiny  fraction of an inch, then

    backed off the adjustment a couple turns  Since readjusting the hangers

    there has not been one noise from the boiler. Odd part, the initial

    tension should not have changed, as there are 5 hangers on multiple

    beams supporting the piping over the boiler which does not have massive

    weight, maybe 200- 250 lbs..
This discussion has been closed.