Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.

If you've found help here, check back in to let us know how everything worked out.
It's a great way to thank those who helped you.
Need to contact us? Visit

Buderus GB142 ... multiple corrosion issues.

woobagoobawoobagooba Member Posts: 45
A noob here, thanks for all the terrific advice. Hoping to get your views on the following. Pics attached.

I've got a new-to-me, approximately 10 year old, natural gas fired GB142 w/ indirect Buderus HW tank. 3500 sq ft house with cast base boards and radiators. The issues ...

- the pump manifold is rotting away. Why? Particularly concerned with the related corrosion within the boiler. I read the manifold is a problematic original, and there was a replacement offered at some point?

- the vent piping seems to be discolored, and the 90 degree elbow just before the turn to go outside the house appears to be leaking. Condensate not draining correctly and caused failure of the PVC cement joint? Seems a slope issue with the exhaust line? Exhaust too hot?

- can't see it in the photos, but their is a hole (1" round ) rotted through the back of the (aluminum?) exhaust vent adapter (no worries, the unit is shut off). It was leaking exhaust directly into the basement! I assume this was a condensate issue. New flue vent adapter kit (plastic) has arrived and is ready to go in.

HX has not yet been disassembled. No idea how often it was cleaned. Probably due for cleaning.

So I'm going through the math repair versus replace. Also need recommendation for good Buderus service tech in Eastern MA.

Much appreciate your opinions on of all this.



  • IronmanIronman Member Posts: 5,682
    I'd say a severe lack of maintenance. No excuse, that's the easiest mod/con to clean.

    Just go through and clean or replace whatever needs it.

    Is there an AM10 boiler reset control? The flue pipe deterioration leads me to believe not. Without it, the high limit on the boiler is 194* which is unnecessary and inefficient.
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • hot_rodhot_rod Member Posts: 13,509
    Check your model number, see if any recalls are open.

    Water quality is critical in aluminum block boilers, a tight ph, below 7 gpg hardness, and chloride level below 100 for the fill water.
    Some installer like to add corrosion inhibitors to protect the HX. Conditioners buffer the ph, introduce oxygen scavengers, and add film providers to protect all the metals. Conditioners do need maintenance and occasional buffers added.

    Here are water specs, and approved aluminum friendly conditioners for one of the newer models.

    If you have a manual check it for cleaning and service info,
    if not, download the manual for your exact model.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • GWGW Member Posts: 3,766
    Seems like you may have anti freeze in the system.

    That pipe is showing corrosion in an odd spot, is there something dripping on it?

    The manifolds have been a pain at times:

    The “flue adapter” has also been a problem. We do a couple a year, 1/d day project

    when we get new customers calling us for GB142 service, we have them read our GB142 letter and acknowledge it. It’s filled with items that can come back and haunt us

    If it has antifreeze and it hasn’t been serviced in a while, start saving for a new boiler.
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
  • woobagoobawoobagooba Member Posts: 45
    edited August 2019
    @Ironman ... yes an AM10 is installed and I see the the outside temp sensor mounted a few feet below the exhaust.

    @ Hotrod. I did locate the Buderus water chemistry guidelines. I will check with the town (I am on muni water), or better yet do a Rhomar test. And also will check on that recall notice.

    @ GW. Unlikely there is antifreeze in system ... I will check.

    PO claims unit was serviced annually in Fall. Service tag indicates it was serviced Fall 17 and 18. I popped open the HX burner fan and condensate collector plate. I ask you, is this one heating season of scale buildup?

  • woobagoobawoobagooba Member Posts: 45
    edited August 2019
    Just noticed corrosion in the condenser plate corners? Cause of the corrosive leak on the supply and return lines to the lower right inside the enclosure?
  • IronmanIronman Member Posts: 5,682
    edited August 2019
    Clean the heat exchanger by spraying mineral oil on it, then turn it on. Avoid getting it on the ignitor and flame rod. Repeat if needed (very likely).
    Get a new gasket for the collector plate and maybe a new trap. Clean they flame rod with a dollar bill or replace it.

    As, mentioned: it's suffering from a severe lack of maintenance. The previous owner may have paid someone to maintain it, but they grossly failed to do so.
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • ZmanZman Member Posts: 5,871
    A few quick thoughts:

    The vent piping in the picture has some issues. One of the pipes is definitely cellular core, confirm that the exhaust pipe is not.
    The vent pipe does not appear to be sloped correctly back to the boiler. Zip ties off of domestic piping is not a proper support. If the vent pipe is yellowed from excessive heat, it needs to be replaced.

    The HX with that level of fouling is and indication of neglect. I would also wager that a combustion analysis has never been performed.

    The water chemistry is critical with that boiler. What are the levels now and what impact has that had on the internals.

    When you consider what it will take to get this boiler back in operation (for a little while before something else goes bad), how does that compare to the cost of installing a new boiler?

    In my experience, 10 years life expectancy is about average for that model boiler (local water quality and maintenance play a huge factor). I would sawzall it out and get a new stainless steel firetube boiler.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • woobagoobawoobagooba Member Posts: 45
    Thank you. Re: the water quality. I intend to have Rhomar do a test. From what point in the system should I extract the sample? The make-up water supply is from the muni water feed.
  • ZmanZman Member Posts: 5,871
    It would be interesting to know what the existing water in your system is like. You should be able to get that from a boiler or purge drain. I would dump the first bit that may contain sediment in order to get a good representative test.
    I would also test the tap water you intend to refill with.
    You can probably get an idea about the tap water chemistry from the water departments website.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Alan (California Radiant) ForbesAlan (California Radiant) Forbes Member Posts: 2,359
    edited August 2019
    Decent video about cleaning the HX:

    These are the parts I require my GB142 customers have on hand:

    HSI igniter 7099006
    ionization electrode 78195
    Cover hinges 7099834

    For Buderus indirects:
    replacement anode rod 7185715690
    manhole cover gasket 87185725380

    All available at
    Often wrong, never in doubt.

    Click here to learn more about this contractor.
  • vilordvilord Member Posts: 34
    edited August 2019
    I have a GB142/24 in my home, and it needs maintenance, including water quality analysis... I was very unimpressed by the last company I had come out to service it (they charged *$600* for annual service?! And they didn't test the water or fix the leaks. that's a quarter the cost of a complete replacement 142...), so I am also curious if there's a good Buderus tech in the area (I'm in metrowest).

    The corrosion on the manifold looks like mine... the combination plastic/rubber fitting between the manifold and the exchanger (where the pipes go through the plastic housing at the bottom of the boiler) are known issues, and mine has had an occasional drip leak as long as I've owned it, which gets worse if the boiler is shut down for a few days.

    I watch craigslist for GB142's and have considered buying one just to have a replacement for when the aluminum HX corrodes through. Mine was installed in 2012, so I figure I've got maybe 3 years before it is junk.
  • woobagoobawoobagooba Member Posts: 45
    Thanks all ... and an update.

    I was able to engage local Buderus support providers and contacted several GB142 owners. Service tech told me the amount of buildup in the HX was normal for a New England heating season, and the service tag record, the original owner, and collection of replaced parts do confirm the unit was serviced last few years. But IMO the minimum was done. It was likely cleaned, but clearly the decaying manifold was not remedied.

    More than one person has told me they have had HX warranty replacement at about year 8, parts and expertise are hard to obtain, etc. I'm on year 11 with a questionable manifold, rotted flue adapter, gaskets needed, indirect tank is not looking good, etc.

    To bring this GB142 up to par will cost several kilo-bucks. I'm working on a heat load calc and pricing out replacement units ... both combi and indirect hw. Trying to go with stainless fire tube.
  • woobagoobawoobagooba Member Posts: 45
    The Rhomar report ... this for the make up water (the system will likely be flushed and refilled as part of reno)

  • woobagoobawoobagooba Member Posts: 45
    Quick update as winter approaches.

    The plan is to nurse this unit through this winter (of premises renovation).

    Flue adapter, condenser plate gasket, and blower fan required replacement. Pitch of the intake and exhaust was corrected.

    Cleaning procedure was performed.

    Unit does fire, but exhaust exited the condensate trap as I neglected to re-fill the exhaust pipe trap (above the boiler) ... remedy that tomorrow.

    The S100 indirect tank is shot.

    Next week I bring in a pro for annual checkup.

    Its been be an education on this mod-con. I'm in a much better position re: decision making for its replacement (likely an IBC, Lochinvar, or Veissman).

    Funny story. One of the local Buderus listed retailer provided a replacement quote ... offering a GB142! Please no!
  • GWGW Member Posts: 3,766
    Very good boiler, for its day. In 2005 it was that of the high priced Viessmann WB1B. Back then the Viessmann’s were huge dollars. Anyway, many people never got the memo that the GB142 needed maintenance, so “poof”, they started acting up and falling apart
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
Sign In or Register to comment.


It looks like you're new here. If you want to get involved, click one of these buttons!