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High pressure in boiler and leaking expansion tank

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Leon888
Leon888 Member Posts: 5
edited January 2022 in THE MAIN WALL
Hi all, my wife noticed our boiler expansion tank was leaking water from a noticeable crack located at the top of the tank.  And from the rusted condition, we suspect it has been that way for a while (pictures attached).  The tank and boiler are both pretty new (about 5 to 6 years old). We are working towards having this expansion tank replaced, but want to understand what might have caused the leak/crack at the first place, so that we can make corrections to ensure this won't happen again after repair. You advises and suggestions are much appreciated!







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  • Jamie Hall
    Jamie Hall Member Posts: 23,524
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    Pressure looks OK. I'm wondering, looking at the picture -- are you sure the leak is from the expansion tank neck, and not just water getting out of the air release from time to time and dripping down the side, around and onto the tank and causing the problem? It could look like that... but I'd not poke at it!

    I know that expansion tanks are hung from the plumbing like that all the time -- but that's a biggish one, and next time I'd give it some support, so it was supporting the plumbing rather than the other way around.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    tommayMikeAmann
  • Leon888
    Leon888 Member Posts: 5
    edited January 2022
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    Thank you, Jamie. Your suggestion for adding a support is great. Who knows, maybe the current installation (lack os support) is one of reason contributed to the breakdown, we'll for sure adding support to the tank when replacing the unit.

    With regards to the crack itself. I'm pretty sure it is at the tank neck (just addd a couple of more pictures), but maybe hard to see as it's pretty rusted. But the water collected in the bucket (picture in original post) is just from last night....so the leak is quite severe.

    On a side note, do you know if the boiler/tank should be manually cleaned on a regular basis? Thanks again!








  • JUGHNE
    JUGHNE Member Posts: 11,085
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    First shut off the power.
    If you shut off the water supply to the boiler, there are 2 ball valves on the cold water line. I would shut off the one near the gauge.

    Screw down the small cap on top of the air vent, above the tank.

    Wait one hour to see if the pressure drops to zero.

    If no noticeable pressure drop.....there may be some as the boiler cools off....then the tank is not leaking.

    As Jamie says probably the auto vent above is leaking down onto the tank.
    The crack may be the paint letting go on the tank.

    Turn water and power back on.
    If you loosen the cap on the auto vent once a day to let air out then you may see some water spurt out.

    If it passes this test you just need a new auto vent.
    wmgeorgetommay
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,710
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    I agree that the auto air vent is leaking water down onto the expansion tank.I would do as @JUGHNE recommended
    tommayMikeAmannSuperTechPC7060
  • Leon888
    Leon888 Member Posts: 5
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    Hi All,

    I wanted to post a quick update & follow-up question and gather your help and insight. While we are waiting for the replacement tank (out of stock in most of stores) to be purchases. The boiler seemed to have stopped working this afternoon, after we observed the tank started to spraying water (as oppose to leaking water. I wonder if this is due to boiler's safety feature had kicked in? Please let me know if this is normal and if anything else I should be shutting down/turning off in the meanwhile? Many thanks
  • Jamie Hall
    Jamie Hall Member Posts: 23,524
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    No, it is very much not normal, and if the expansion tank is actually spraying water you really can't run the system at all, since you can't run the system with the tank closed off -- if the pressure is remotely right cold, it will be much too high when it heats up.

    The expansion tank may be out of stock in most stores -- but State Supply has them.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Leon888
    Leon888 Member Posts: 5
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    Thanks @ Jamie Hall. So to clarify, you're saying it is normal for the boiler to shut off on its own given we have an expansion tank out of order (spraying water). Hence once it's been replaced, things should return to normal, maybe, hopefully? We noticed boiler temperature had dropped substantially and concluded it stopped working since earlier today. Will check out State Supply. thank you!
  • Jamie Hall
    Jamie Hall Member Posts: 23,524
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    Be happy. The boiler may have shut itself off on its low water or low pressure cutout.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Leon888
    Leon888 Member Posts: 5
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    @ Jamie Hall. And you believe the low water /pressure might have been caused by the leaking expansion tank? sorry i'm very ignorant on these as we are new homeowners. I just hope the water pipes will survive the cold days ahead...
  • SuperTech
    SuperTech Member Posts: 2,197
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    @Leon888 The spraying water may have caused an electrical component to fail. Given the rising number of issues it may be time to call a pro.
  • JUGHNE
    JUGHNE Member Posts: 11,085
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    Looking at your first picture....you have a "Guard Dog" low water cutoff control.

    This device probably saved your boiler from dry firing itself to ruins at best.....
    at worst catching something on fire or possible explosion if you had suddenly added water to a red hot boiler.

    After you get the tank replaced, open the water valves and fill the system.
    There may be a reset button on that Guard Dog that you need to push when you get water in the system.

    This posting is a good example of the necessity of having LWCO on all boilers.