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Expansion tank failing from the middle?

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Javelin
Javelin Member Posts: 138
Dear Heating Pros, about six years ago (with a GREAT deal of help from this forum) I put in my own boiler system.. All has been working well, but just this week, the expansion tank seems to have failed. Odd thing is that it "sounds" normal if I bang on the sides, and the water is NOT coming from the top/bottom, but rather from a size small pit it seems (see attached with inlaid close-up). It's a pretty continuous small dribble out of it.. barely noticeable (except for the water on the floor) unless I put my finger in the way of the dribble..

Has anyone seen this type of thing before? I'm guessing I need a whole new tank, but it's only 6 years old.. Is that an average life span?

The tank I have is:
https://www.supplyhouse.com/Amtrol-118-27-SX-30V-Extrol-Expansion-Tank-14-Gallon-Volume-7365000-p

Also, I note that the PSI of the heating system is 15psi, which I gather from this forum might be a bit low (18 being ideal?) - how would I adjust this? House pressure is 80psi and I have a back-flow preventer and fill valve:

https://www.supplyhouse.com/Watts-0386462-B911S-1-2-Bronze-Combination-Fill-Valve-Backflow-Preventer-Sweat#product-overview

I'm guessing I'd adjust it with this fill valve somehow? Just not sure how.

Thank you in advance for your guidance!

Jay

PS - I've also attached an illustration of my system should it matter...





Comments

  • kcopp
    kcopp Member Posts: 4,444
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    I have seen it many times. What is your radiation that you need that large a tank? Do you have any non barrier pex tubing in the system?
    mattmia2
  • Javelin
    Javelin Member Posts: 138
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    Thanks Kcopp! I have a larger 3 story house with old, big 100 year old cast iron radiators. No pex at all in the heating system.

    So I'm guessing I need a new tank. Have you seen them fail in 6 years or is that unusual? The system still seems to be operating with this small leak and I'm planning on letting it until the new tank comes in. Anything wrong with that? The leak is going into an unfinished basement with floor drain.
  • nicholas bonham-carter
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    Maybe air is getting into this system, and rusting out the tank?
    Is the piping correct—pumping away and all that?—NBC
    Alan Welch
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,724
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    @Javelin
    Yes change the tank. I just replaced mine last year it was in the house when I bought it and that's 31 years.

    18 psi sounds right for a 3 story house you should have 4-5 psi static pressure at the top of the house with the pump off.

    Check for leaks in the system.
  • delta T
    delta T Member Posts: 884
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    Usually I this on systems that have water quality issues or constant fresh water being added due to a leak somewhere. Even a very small leak can cause this.
    HomerJSmith
  • Javelin
    Javelin Member Posts: 138
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    Thanks everyone.. I've ordered a new tank - should be here tomorrow.. I haven't seen any leaks at all anywhere, but I have drained the system a few time to remove radiators for renovation here and there.. Maybe my Spirovent isn't doing it's job anymore.. (I ordered a new spindly/wire insert for that too).

    If 18psi is correct for the system, how do I raise it from 15 to 18? Is there a setting usually on the water makeup valve?
  • Zman
    Zman Member Posts: 7,588
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    You will want to precharge the tank to 18# using the Schrader valve. Your system fill valve will a nut or screw you turn. Post a picture or look in the manual.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Javelin
    Javelin Member Posts: 138
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    Thanks Zman.. so I think I did both - increased the pressure of the system through the fill valve and also pumped some air into the expansion tank.. it seems the pressure goes a bit higher when the boiler is heating though.. could that mean that the pressure in the expansion tank is too high?
  • Intplm.
    Intplm. Member Posts: 2,035
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    @Javelin Be careful not to scratch the paint when installing your new tank. It appears the old tank was scratched and , believe it or not, this can greatly contribute to the tanks leaking and early failure.
    Your leak seems to have started from the "outside in " and not from the inside out.
  • Javelin
    Javelin Member Posts: 138
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    Thanks Intplm... that silver streak thought is/was some wayward solder I think think from a sweat joint above sometime that wasn't cleaned up... still.. thanks for the advice.. the new one is in unscathed.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,153
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    you will need to use a tire pressure gauge to check the tank pressure. the system pressure will need to be lower than the tank air pressure EMPTY. This is because the air can't leave the tank thru the bladder. if you have 20 or 25 lbs. of water pressure in the system, then your tire gauge will read that 20 0r 25 # water pressure because the water pressure will compress the air on the other side of the bladder to match the water pressure.

    once you reduce the water pressure in the system below the air pressure in the tank, you will know the actual air pressure. Get the pressure in the tank to 18 PSI by adding or removing air as needed. Then put the water pressure back on to match the air pressure. This will provide the best balance of air pressure and water expansion. Your operating pressure may change slightly but 5 psi or less is acceptable.

    100 gallons of water at 70°F will increase in volume to 105 gallons at 220°F. That extra 5 gallons will go into the expansion tank if there is room (that is the air space on the other side of the bladder) and the pressure will only increase by 1.5 psi. If the tank air pressure is too high, the pressure in the boiler must increase to the air pressure in the tank before the extra 5 gallons can begin to enter the expansion tank.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    ethicalpaul
  • Jolly Bodger
    Jolly Bodger Member Posts: 209
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    With all that cast iron in the system, are you using any water treatment?
  • Jolly Bodger
    Jolly Bodger Member Posts: 209
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    Expansion tanks fail all the time. Usually it is the bladder, not the shell. This is caused by not maintaining the pressure in it. Expansion tanks should be drained and the pre-charge checked every year. Most never are.
  • hot_rod
    hot_rod Member Posts: 22,334
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    I'd second the use of conditioner in ANY hydronic system with ferrous metals. They offer so much needed protection for systems.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Javelin
    Javelin Member Posts: 138
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    Thank you all.. I drained the tank, pressurized it to 18psi and put water into the system until the boiler read 18psi (while it was cool). So I'll keep my eye on it..

    No, my system doesn't have any conditioner in it that I know of. What sort of thing should I be considering? I thought since the water had all it's air pulled out of it, that it wouldn't be too much of an issue.. no? These radiators are over 100 years old though, so am open to any suggestions to keep them cooking!

    Thanks!
  • hot_rod
    hot_rod Member Posts: 22,334
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    My opinion is the film providers in the hydronic conditioner chemicals are a key component. They provide a few micron thickness layer of protection to new and bare metals. Think of it as a thin primer layer on bare metal.
    This protects against corrosion and attack from aggressive water, low ph, high ph, high chloride levels, etc. are all examples of corrosive water conditions. To me it is a cheap insurance to give the components the best opportunity to live a long happy life.

    I have been suspicious of upside mounted tanks and those base mounted tanks in that they can trap some air, along with it O2 content in the lower portion. the1 O2 looks to oxidize the bare metal, tense the rust pitting potential. The very thin gauge metal used in expansion tanks is compromised from day one.

    The aerosol can inhibitors sold now make it super simple to add the protection to new or old systems. Connect to a hose thread, pull the trigger, task completed.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    rwhtg
  • HomerJSmith
    HomerJSmith Member Posts: 2,476
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    You might try 1 gallon of Rhomer PRO-TEK® 922 in your sys with good fill water.
  • Javelin
    Javelin Member Posts: 138
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    Thanks Homer, so this:

    https://www.houseneeds.com/heating/hydronic-heating-boilers/rhomar-hydronic-boiler-treatment-corrosion-inhibitor-922

    about $57 plus shipping? Will it be clear how to put it into my system?
  • hot_rod
    hot_rod Member Posts: 22,334
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    This kit here treats 35 gallons, cleaner first, then inhibitor. No sense putting good conditioner in a dirty system.
    It may be easier to use this kit and you could buy 2 if the system is large.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Javelin
    Javelin Member Posts: 138
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    awesome.. thanks!