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Thread: Expansion Tank for a Hot Water Heater

  1. #1

    Default Expansion Tank for a Hot Water Heater

    I am replacing a HWH and would like to add an expansion tank.

    Question 1: I am not having problems with my current system, should I install one?

    Question 2: The directions call for the tank to be mounted with the 3/4" fitting at the top or hanging by the fitting. I don't have the room to install per directions. Will it hender operations for the tank if I install it with the fitting on the bottom or "reverse" of the installation directions?

    Thanks for your help....Dan

    http://www.watts.com/pdf/1915356.pdf
    Last edited by Terry; 10-27-2008 at 11:27 AM.

  2. #2
    Plumber Cass's Avatar
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    Unless you have a Pressure Reducing Valve and / or a check valve you don't need one...

  3. #3
    Retired Defense Industry Engineer jadnashua's Avatar
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    The tank will work in any orientation. When it eventaully fails, if it is on top of the fitting rather than below it, you'll have a tank full of water trying to come out while you remove it. Depends on how well you can drain the pipe system as to how messy it would be.

    But, as mentioned, unless you have or intend to install a PRV, or have a checkvalve in the system, you don't need one. Note, water districts may change their meters and the new ones could contain a checkvalve. Having an expansion tank won't hurt if you don't currently need one, but it won't buy you much except the expense to install.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    In the Trades Gary Swart's Avatar
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    When water heats it expands and needs somewhere to go. If you have an open system, that's one where you do not have either a PRV or a check valve in the meter, this expansion is absorbed by the city water main so you do not need an expansion tank. If you do have a PRV or check valve, this is called a closed system and the expansion has no place to go. This results in a very rapid pressure increase in the water heater and when the pressure reaches 150 psi, the T/P valve on your heater will open to relieve the excess pressure and prevent the heater from blowing up.

  5. #5
    Radon Contractor and Water Treatment 99k's Avatar
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    Do you have a well? If so, your present pressure tank will do the job.

  6. #6
    Moderator & Master Plumber hj's Avatar
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    Default tank

    YOu can install the tank in any direction, AS LONG as you support it by something other than the pipe connection.

    http://www.watts.com/pdf/1915356.pdf
    Last edited by Terry; 10-27-2008 at 11:28 AM.

  7. #7
    Apprentice Plumber D'Brie's Avatar
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    Quote Originally Posted by Gary Swart View Post
    When water heats it expands and needs somewhere to go. If you have an open system, that's one where you do not have either a PRV or a check valve in the meter, this expansion is absorbed by the city water main so you do not need an expansion tank. If you do have a PRV or check valve, this is called a closed system and the expansion has no place to go. This results in a very rapid pressure increase in the water heater and when the pressure reaches 150 psi, the T/P valve on your heater will open to relieve the excess pressure and prevent the heater from blowing up.
    +1, This is the way I have been taught also.

  8. #8

    Default

    Ok, I have a well and for various reasons I ended up installing a check valve after the pressure tank. Now I know I'm supposed to install an expansion tank and I will when I relocate my HW heater shortly (basement remodel), BUT I have never, not even once, seen my pressure gauge after the check valve read anything but a couple of PSI LOWER than the one located on the bladder tank manifold.

    Like I said I'm still going to install the expansion tank because I know its supposed to be there and that heating water causes an increase in pressure, but just once I'd like to see it read even 5 PSI higher.

  9. #9
    Plumber Cass's Avatar
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    Why is there a check valve there...I would remove it...that will be a lot easier and less expensive than a Exp. Tank.

  10. #10
    Master Plumber nhmaster's Avatar
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    Prv, check valve, meter with check valve makes no difference. The code requires an expansion tank on all water heating pressure vessels.

  11. #11
    Plumber Cass's Avatar
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    he is on a well...if he removes the check valve he has a very large expansion tank.

  12. #12
    Master Plumber nhmaster's Avatar
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    The code does not say a well can be substituted for an expansion tank, besides which there is a foot valve down there somewhere.

  13. #13
    Plumber Cass's Avatar
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    Quote Originally Posted by nhmaster View Post
    The code does not say a well can be substituted for an expansion tank, besides which there is a foot valve down there somewhere.
    So you would put an expansion tank on a well system that had a direct, non checked, cold water path to the bladder tank from the water heater, that is what you would do?

    Now hear me, I am asking you what you would do.

    I have my hand on my helmet...getting ready...
    Last edited by Cass; 10-27-2008 at 07:47 AM.

  14. #14
    Moderator & Master Plumber hj's Avatar
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    Default tank

    It would be an unusual system if it had the foot valve between the tank and the water heater. The storage tank IS a large expansion tank, regardless of whether the codes call it that or not. The only way it does not meet some regulations is that it is not between the heater's cold water valve and the heater.

  15. #15
    Master Plumber nhmaster's Avatar
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    I would absolutly put an expansion tank in. The code never asks for my opinion or how I feel about things. The words "shall" hold up in a court of law. Do I agree with putting a tank in? No, but because I am constantly worried about laibility (and so should you all be) I do everything to code. Then there's no questions, no arguments, no liability.

    HJ there is a foot valve at the bottom of the well drop if it's a shallow well pump and a check valve on top of a submersible pump.

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