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Thread: WH Expansion tank rust-through?

  1. #1
    DIY Junior Member
    Join Date
    Dec 2007
    Northern VA

    Default WH Expansion tank rust-through?

    I have a newish - 2-3 year old max - water heater expansion tank
    that has developed 3 rust holes, one of which has started leaking.

    Why the rust spots (and the hole)?

    The expansion tank is a State Industries Inc 2 gallon tank. I got
    from a local plumbing supply place. The Model is ETC2X.

    I'm figuring it will be a warranty replacement. How can I tell how
    old it is?

    The actual leak just started today, but the spots have developed
    over time no doubt (I can try to upload some pictures tomorrow night
    after work).

    What would cause such an issue? Terribly corrosive water eh? Nothing
    out of the ordinary in the was "tested" with a DIY kit from the
    local Home Depot. We'll have to have this checked by a seasoned
    professional (vs water filter sales type - suggestions would be
    helpful for a reputable testing outfit, in Northern VA), but nothing
    else has been an issue in 4.5 years at this house.

    The tank is a horizontal mount above a Ruud PH50 50 gallon gas
    fueled water heater that is a 1002... serial, which I think
    translates into October 2002 manufacture. So it is 5.5 years old,
    thusly replaced a year before we moved in.

    In-house water pressure is 39 - lowish, but it serves the house
    well. I do have a new Pressure Reduction Valve on the main. The
    old was stuck at 50psi & in close range to a poorly done whole house
    filter (with no filter in it), that had cutoffs that were not full
    flow valves - lack of flow was an issue. This change was about 4
    weeks ago - I don't think lower pressure would cause sudden expansion
    tank rust (?). You'd think I would have noticed the rust streaks
    across the tank when I did the PRV?

    Why is this expansion tank just a few years old? The blue (I don't
    have details on it other than I recall it was blue) tank that was
    installed got a pinhole - no visible sign of rust. It was just a
    tiny itty bitty hole in the inlet end that was squirting a tiny
    stream of water at the wall (lotta good a pan does for that sort
    of issue). This tank looked good - probably installed with
    the Ruud - so it failed even sooner than it's replacement,
    but with no visible rust (I should have kept it and cut it apart,
    depending on warranty value of current one, I'll plan to cut
    it apart).

    So - tomorrow off to supply for some exchange (?) or big box to
    find another ... or, to diligently research tankless water heater.

    If I have multiple choices of brand, what would be recommended?

    Any other recommendations - besides a water test pronto?

  2. #2
    Master Plumber master plumber mark's Avatar
    Join Date
    Feb 2005
    indianapolis indiana - land of the free, home of the brave....
    Blog Entries

    Talking change it asap

    39 psi is pretty low, but if you are happy... whatever.....

    you really ought to change that expansion tank asap...

    most state brands are really not that good and I have known
    of a couple of catastrophic floods due to them and other brands
    blowing a penny sized hole out the side of it....
    in a totally flooding a finished basement....

    you dont want that to happen.

    the only good thing was I was not the fellow that
    did the original install....so it was not on me to do the clean up...

    I do install them ......but the customer never sees the need to
    maintain them after the fact..... and on averrage they will outlast the heater anyway..

    but you got a nasty one that can deal you some nasty greif
    it you dont move quickly

    try a amtrol.....

    here is some info on tankless


  3. #3
    DIY Junior Member
    Join Date
    Dec 2007
    Northern VA

    Default changed tank ...

    One local supply had the Watergaurd - not that again, the
    other had a Watts (PLT-5). Neither had the Amtrol as

    I'll keep an eye out for one & buy it as a spare :-) Later today
    might be cut-it-open time for the old one.

    And as a reminder, I wrote on the new one when I put it

    Thanks for the reply!

    Also - on tankless - Thanks for the link. That would be way future
    when the current WH dies, them tankless things
    are expensive, and I'd have to experience one for myself.

  4. #4
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    Just make sure the expansion tank you got is for potable water and not designed for a boiler.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  5. #5
    In the Trades Gary Swart's Avatar
    Join Date
    Sep 2004
    Yakima WA


    What is the water pressure on the city main? It sound to me like either your PRV is set too low or perhaps you don't even need one. If the city main pressure is less than 80 psi, I'd pull the PRV and expansion tank out...you don't need them. If you do need to reduce the pressure with a PRV, make sure it is working OK and crank the pressure up to 50 or 60 psi and get an new expansion tank. If you have a PRV, you must have an expansion tank also. If you don't have your own pressure gauge, you should get one at any hardware store for $12-$15.


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