Water heater expansion tank

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by igornys, Oct 8, 2013.

  1. igornys

    igornys New Member

    Messages:
    14
    Location:
    New York
    Expansion tank on my 50 gallon water heater become full of water so that I decided to replace it ordering the same model (Therm-X-Trol ST-12) that I had before.

    The tank was installed horizontally above the heater (see below). Now when reading installation manual, I see that according to the manufacturer, the tank has to be installed vertically.


    Schema.jpg

    What would you recommend?

    My plans is to change the tank location as showed at the picture on the right as there is a wall on the right of the water heater so that I can provide support for another end of the pipe easily.

    Also, when installed this way, the bottom of the tank will be below the top of the water heater (see second picture below), is this permitted?
    new_1.gif

    Thanks a lot for the response
    Last edited: Oct 8, 2013
  2. Gary Swart

    Gary Swart In the Trades

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    Location:
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    If that is what the installation directions say, I can't argue that point. However, the installation for thermal expansion tank I have allowed for it to be installed as your old one was. The main caution with any installation was to be sure there was a good support. The drawing you have with the tee would work. Mine is just a tee in the main line with the tank suspended below. The main line is strapped to floor joints. The height is of no concern.
  3. Terry

    Terry Administrator Staff Member

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    You mean this part of the instructions?

  4. igornys

    igornys New Member

    Messages:
    14
    Location:
    New York
    Terry, Gary,

    thanks a lot for the quick response.

    I was looking at the on-line installation instruction provided by Home Depot.

    The limitation is described in the section on the left, last sentence in the warning #5. Please note, that PDF manual was revised on 8/06 (see on the bottom).

    After your response I compared it with the printed instruction that came with the tank (dated 11/11) and this very last sentence about the position is missing there … Also, instruction available at Amtrol directly does not have this limitation.

    I assume that the modern Amtrol tanks can be installed in any position.
    Last edited: Oct 8, 2013
  5. Terry

    Terry Administrator Staff Member

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    I called Flexcon, the brand that I mainly install, and they say the Flex-ST5 can be mounted horizontal as long as it's supported.
    They don't want the dead weight putting pressure on the pipe.

    I either go vertical with fittings off the water heater, or if I wall mount the expansion tank horizontally; I strap it.

    [​IMG]
    Last edited: Oct 8, 2013
  6. igornys

    igornys New Member

    Messages:
    14
    Location:
    New York
    Terry,


    Terry,

    thanks a lot for the response - I actually installed support when replacing tank earlier today.

    My major concern was weight in case tanks is leaking/become full of water. Specifically in my case the tee has 1/2 “ connection when my Amtrol tank has 3/4" connector so that I had to use an adapter increasing the lever.

    WaterHeater1.jpg
    Last edited: Oct 8, 2013
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    22,313
    Location:
    New England
    If the strapping is installed well, it should be more than sufficient to hold the tank in position when it eventually fails. They all do, eventually, but it depends on the water quality and how well you maintain the pressure so the bladder doesn't get stretched to the limit. Since it's close to he wall, you could put a shelf bracket underneath it...some I've seen (and use in my garage to hold some lumber) are rated at as much as 1/2T...any 'normal' one should be more than enough as a backup, should you not trust your strapping.
  8. igornys

    igornys New Member

    Messages:
    14
    Location:
    New York
    Strapping should perfectly hold 4 gallon tank even if full of water, but as a former Defense Industry Engineer :),  I don’t trust mounts that have extra degree of freedom. The wall is unfortunately a bit too far to use a shelf bracket to support.

    As for the tank itself, the previous one was installed ~1 month ago by a plumber who replaced the old water heater and the original Amtrol tank. Not pre-charged + almost 90 psi water pressure made it failed soon (the tank installed was not Amtrol, but some noname ).

    This is why I started looking on-line to better understand what was done wrong. I hope I did it right now, also pre-charged and lowered the water pressure.
  9. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
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    Location:
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    I prefer to mount the tank vertically, above or below the pipe, directly into a tee so there is no lateral stress on the connection. But, if it is supported properly, it can be located in any position. I also put a valve on it so it can be service or removed without shutting off the water and draining pressure out of the system.
    Last edited: Oct 9, 2013
  10. igornys

    igornys New Member

    Messages:
    14
    Location:
    New York
    How often do you typically replace the expansion tank?

    As for the service/pressure maintenance – indeed having a separate valve would be more convenient.

    I assume, however, that closing the incoming could water to the heater/opening hot water faucet at the location nearby for a couple of minutes will be enough to measure the actual tank pressure.
  11. Terry

    Terry Administrator Staff Member

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    15,413
    Location:
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    I would like to watch you replace an expansion tank without draining off the pressure first.
    That thing holds about two gallons of water at house pressure.
    I think someone is going to be pretty wet.
    Last edited: Oct 9, 2013
  12. Reach4

    Reach4 Well-Known Member

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    He used a valve with a drain, and he remembered to put the drain on the correct side. :) [​IMG]
  13. DonL

    DonL Jack of all trades Master of one

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    Houston, TX

    I would hope She is wearing a T-shirt and no bra.
  14. Terry

    Terry Administrator Staff Member

    Messages:
    15,413
    Location:
    Bothell, Washington
    Well...............that tiny little pin hole will take a while to drain 2 gallons under pressure.
    I've seen the ball valves for that connection before, but then I think about how much water is trapped in that tank, and I think about the dunking I would take spinning it off.
    The small drain there, I guess you can stand there with a bucket and try to catch it without getting wet as it's spraying at you under 60 PSI pressure.
    I would rather shut shut the water heater off and open a faucet.

    And Don, I just wear a T-Shirt.
    Last edited: Oct 9, 2013
  15. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,313
    Location:
    New England
    FWIW, while I like having one there, having a valve between the ET and the WH is not code. You could forget to open the valve, and then the ET is essentially useless. If the ET has failed, then at least if it was hanging vertically, you'd not have any water under any real pressure...you might not get wet taking it off. Horizontally, is another issue.

    Also, if your static WP is 90psi, you should add a PRV! Residential settings are required to be NGT 80psi.
  16. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
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    Location:
    Cave Creek, Arizona
    IF the tank is set at the house pressure, there will be little, if any, water in it.
  17. Terry

    Terry Administrator Staff Member

    Messages:
    15,413
    Location:
    Bothell, Washington
    That's not how it works in Seattle.
    Here, when you have an expansion tank, and turn the water off, it takes a while for the water to quit draining. It's like a delayed shutoff.
    Without the expansion tank, off is off.
  18. Reach4

    Reach4 Well-Known Member

    Messages:
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    Location:
    IL
    I laughed at that one.

    Then I thought, what if the tank was pre-charged with 60 PSI of air and the city supplies 60 PSI water? Maybe that tank would do a better job of being able to accept over-pressure water, as the water heated, than if the tank was pre-charged with less.
  19. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,313
    Location:
    New England
    That's how they are supposed to be installed...set the precharge to your NORMAL water pressure, then the bladder is at equilibrium, providing the full capacity of the tank, and not having to be stressed as much by overstretching it. Now, when the WH causes the water to expand, it has the full capacity of the tank to absorb it. When you open a tap, the ET will release the water it is storing, and be ready for the next time the WH is running.
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