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Replacing old style expansion tank

tombstone Member Posts: 30
I have a leaky valve at my old style expansion tank and have decided to remove it and replace it with a new bladder style tank.

The issue I have concerns the need or requirement for an air separator. The supply piping from my boiler is 1" and is mainly vertical. It turns 90 degrees at the floor joist and continues along to feed the radiators. The 90 degree fitting has a 1/2" fitting coming out of it at the bend. The old expansion tank it connected to a piece of 1/2" pipe that connects to this fitting.

My plan is to remove the 1/2" pipe and expansion tank and repipe with 1/2" to where I want the new expansion tank to hang. From there I'll sweat on a 1/2" NPT adapter and ball valve.

There is an air elimination device on the 1" pipe a few feet from the boiler.

Does this seem like a suitable plan of attack?




  • Gordy
    Gordy Member Posts: 9,537

    Is your circulator located before or after this point where you have the x-tank?

    As far as the x- tank performing its function your fine. Pumping away from the point of no pressure change(the x-tank) your circulator should be down stream of this point. In your case the elbow where the x-tank will be plumbed in.

    Having the circulator in this location will facilitate air removal more, and prevent a sub atmospheric condition allowing air into the system.
  • Ironman
    Ironman Member Posts: 7,119

    You should not have an air vent there with the old style tank. Air was intended to be removed from the system by allowing it to enter the expansion tank and thus the tank would maintain its air cushion. It's an either or situation, but not both. You either have the "open" tank and no air separator or a bladder tank with an air separator. Of course, an auto vent is not an air separator (MBR), but it should not be there with an open tank.

    If you're going with a bladder tank, then you need to install an MBR (micro bubble resorber) like a SpiroVent or equivalent, or a scoop at minimum. Connect the expansion tank to the bottom port of the MBR and place the circ directly down stream of it as Gordy suggested.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • tombstone
    tombstone Member Posts: 30
    Circulator Location

    The circulator is located on the return side of the boiler.
  • tombstone
    tombstone Member Posts: 30
    Air Vent

    To install a standard Spirovent will prove to be rather difficult do to how I'm currently piped. Most all of the 1" pipe (I think) is vertical.

    I have found this http://www.pexsupply.com/Spirotherm-VJV100-1-Spirovent-Jr-Vertical-Air-Eliminator-Threaded-9309000-p that would work in my application and allow me to place the expansion tank where I previously suggested.
  • Rich_49
    Rich_49 Member Posts: 2,721
    edited October 2013

    air elimination devices can be found through Caleffi and Spirovent .  Plug the fitting that the air vent is presently in and also the supply tee at top then add the new unit above your cold water inlet and pipe to the new tank out of a second tee that you will locate between the new eliminator and cold water .  Pretty easy  
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
  • tombstone
    tombstone Member Posts: 30
    New Piping Diagram

    I wanted to make sure that I am understanding correctly and attached a new drawing of what I think I'm supposed to do.

    Will there be any issues with the "t" at the top just being plugged? I was concerned that it could be a place for air to collect.

    Thanks for all the help!
  • jumper
    jumper Member Posts: 2,059

    Why not fix or replace the valve? The old style lasts forever but when the rubber goes....
  • tombstone
    tombstone Member Posts: 30
    Final thoughts?

    I'm planning on tacking this tomorrow and was looking for any additional comments on my sketch of what I'm planning on doing.

This discussion has been closed.