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  1. #1
    Join Date
    Nov 2018
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    Expansion Tank Replacement (?)

    Hi All,

    My first post here!

    I have a Navien tankless boiler and have noticed a small leak originating from the Pressure Release Valve.

    When I tap on the expansion tank it sounds fairly full.

    With the exception of tasks that require a certified professional (such as gas installation), I like to perform as much maintenance on my own in order to get better understanding of how things function (metallurgical engineer by training).

    I'd like to tackle this project on my own but wanted to confirm the procedure:

    1. Shut off power to the boiler
    2. Close the water inlet to the boiler
    3. Close the water outlet from the boiler to the radiators
    4. Drain the water remaining in the system -- essentially what remains in the pipes between the inflow and outflow shut-off
    5. Remove the failed expansion tank (I understand it may be quite heavy)
    6. Install a new expansion tank (using teflon thread tape)

    And now here's where I'm unsure -- should I be:
    1. Turning on the boiler
    2. Opening the inflow to the boiler and then
    3. Opening the outflow

    Will this introduce air into the system that I need to bleed out from radiators?

    Also, I believe the pressure relief valve looks okay, but I'm thinking since I'm going to all this trouble I may as well just replace it as well.

    I've attached photos of my system.
    Attached Images Attached Images

  2. #2
    Join Date
    Jan 2010
    Posts
    17,359
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    Is there not a air port on the bottom of the expansion tank ?

  3. #3
    Join Date
    Nov 2018
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    Thread Starter
    No, there is no port on the bottom of the expansion tank that is currently installed (Watts ET-30). I'm leaning towards replacing it with an AMTROL EX-30.

    Are you asking for the purpose of re-charging it with air or to bleed the system out?

  4. #4
    Join Date
    Jan 2010
    Posts
    17,359
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    Had there been one you could check for water leaving that port.
    Is yours piped this way ?
    Attached Images Attached Images

  5. #5
    Join Date
    Nov 2018
    Posts
    4
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    Thread Starter
    Interesting. So the hydronic circulator is on the System Supply?

    If this is the case, then my expansion tank appears to be on the System Return from what I can see.

    Does this mean the Extrol EX tanks are not suitable for my application?

    I have a video on Youtube of the system but I'm not allowed to share the link until I post 4 more times

    THANKS!

  6. #6
    Join Date
    Nov 2018
    Posts
    4
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    Thread Starter
    Here's the link:

    youtu.be/OxSaguLelGo

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