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Discuss Expansion Vessel Upside Down? in the Central Heating Forum area at

  1. hallra

    hallra Member


    Has this expansion tank been installed upside down?
    - The cold water expansion tank is install this way as well...

    Or is there something special about the configuration that I haven't understood?

    Surely air gets trapped with the expansion tank fitted this way?

    I still have noise in my top radiators, I am bleeding everyday and I'm scratching my head trying to find the cause.
    - FYI: An Air Seperator is on order.

  2. Harvest Fields

    Harvest Fields Trusted Plumber GSR Top Contributor!!

    Nope. It is the correct way around. Just make sure it is on the heating circuit and not the hot water though. As grey is not for potable water.
    • Agree Agree x 5
  3. hallra

    hallra Member

    Hi Harvest,

    Thanks for your reply.

    Yep it is on the heating side.

    I don’t understand then, how does air not get trapped, as the expansion tank is on a long run of pipe work, with it being the highest point.
  4. Riley

    Riley Plumber GSR Top Contributor!!

    It’s right
    • Agree Agree x 1
  5. townfanjon

    townfanjon Trusted Plumber GSR Top Contributor!!

    TYI pal , some potable vessels are grey , but yes generally white .
    • Informative Informative x 2
    • Agree Agree x 1
  6. Harvest Fields

    Harvest Fields Trusted Plumber GSR Top Contributor!!

    Air is supposed to be trapped mate. (For expansion purposes).
  7. JVTrades

    JVTrades Member

    You're getting confused with an open vented header tank I think. With a bottle like this there should always be air in the bottle. The normal issue with these though is that the air pressure in it is not maintained correctly and should be checked annually at least. As the pressure in the tank increases and the water expands the expansion pushes into the bottle which has an air pocket in it, when a tap is opened any water in the bottle gets pushed back in to the system. If the air pressure in the bottle isn't maintained then this bottle can be completely full of water and when the pressure in the system increases the water has nowhere to go and the pressure relief valve at the bottle will open to get rid of the pressure. The problem then is that they normally never close properly and need to be replaced.
  8. hallra

    hallra Member

    Sorry I didn’t explain myself properly.

    There is a diaphragm within the expansion vessel, one side has air, the other side, the system side, has water.

    The point of the air side is to allow the expansion of the water on the system side, without a significant pressure increase.

    My question was what if air was trapped on the system side, therefore air on both sides of the diaphragm, would this cause a problem?
    - Air would presumably be trapped if the system has been emptied of water and then refilled, as there is no way of bleeding that part of the circuit, as only one pipe to the expansion vessel.
    - I know there is another pipe but that route is blocked by the safety value.

    I’m asking these maybe dumb questions as I’ve got a lot of trapped air in the sealed heating system that should not be there and I can’t work out what the cause is.
    - I’m bleeding daily two radiators upstairs and they constantly have good amounts of air in them very soon after they have bleed, as a consequence there is a lot of noise being produce.

    I have tried many things to resolve and still I have a problem, next try is an air separator.
    • Creative Creative x 1
  9. hallra

    hallra Member

    I have some video on my phone of the noise produced, but it seems I can’t upload them.
  10. Harvest Fields

    Harvest Fields Trusted Plumber GSR Top Contributor!!

    Think videos need to be uploaded from an actual computer
  11. Riley

    Riley Plumber GSR Top Contributor!!

    I would say next to no chance of that being the problem. All manus recommend installingthat way
    • Agree Agree x 1
  12. hallra

    hallra Member

    Yeah I know, I’m clutching at straws, this has been going on for weeks and I’ve tried so many things I’ve got desperate.
    - I’ve had a plumber look at it who couldn’t find anything wrong.

    I’ve just had an email from someone at Altecnic, they have offered to talk through the problem in detail with me to see if they can work out the cause.

    - A lot of the system components are from Altecnic/Caleffi, so I had sent them a speculative email.
  13. Riley

    Riley Plumber GSR Top Contributor!!

    My advice see if they have a recommended technician
    • Like Like x 1
  14. Pickwickpick

    Pickwickpick Top Contributor!!

    The expansion vessel won't be the source of your problems, any air that does end up in it from the CH water doesn't cause any issues as it acts in the same way as the air behind the bladder, there's no way you'd get enough air in there to alter the performance of the vessel and it wouldn't cause any noises.

    With regards to the having to constantly bleed your rads, is this a new system? Have you had any alterations made to an existing system? Has an inhibitor been added?
    • Like Like x 1
  15. Best

    Best Trusted Plumber Top Contributor!!

    I am going to contradict the thinking a little by saying that a heating system vessel ideally should be fitted with water side upmost.
    Many diagrams also show them fitted with water connection upmost and straight into heating pipework, or if a high spot then an auto vent shown fitted.
    But it doesn’t seem to matter which way you install them
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