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Discuss Expansion tanks - background info in the Plumbing Forum area at

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  1. TaylorBL

    TaylorBL New Member

    Hi all - Apologies for intruding, but I was curious if you wouldn't mind helping me better understand the use and preferences related to expansion tanks/vessels in your area. I'm tasked with learning how they compare to use in the United States.

    - Are expansion tanks common in your area? Will there certainly be one if household has a boiler/water heater?
    - Are they mandated by any regulations?
    - What brands are the best in your opinion? Or does brand not matter?

    Many thanks!
  2. SimonG

    SimonG Trusted Plumber

    Have a read up on vented heating systems and sealed heating systems.
  3. TaylorBL

    TaylorBL New Member

    Sorry, I wasn't very clear. I'm well-versed on the benefits and function of expansion tanks but only in the United States. What I'm trying to understand is how large the market is in the UK (whereas in the US it's inconsistent based on municipal regulation and homeowner preference) and what brands you have over there. Appreciate any help.
  4. SimonG

    SimonG Trusted Plumber

    Zilmet is popular.

    Basically whatever is on the shelf.

    It's an age thing over here. Older systems tend to be open vented and newer ones sealed. But even that statement can vary.
  5. rpm

    rpm Trusted Plumber

    Taylor, what would you say is the average size tank in an average house your side of the pond and welcome to the forum.
  6. chris watkins

    chris watkins Plumber

    We tend to call them expansion vessels when used in heating & domestic hot water systems.

    There is no regulations as such, almost all new systems will be sealed & require one but the majority will come pre-installed as part of the boiler.
    Combination (combi) boilers which provide heating as well as domestic hot water & system boilers which just provide heating but come complete with the vessel.

    Some old open vented systems are converted & have a vessel & safety valve installed but it is not many.

    Vessels are also installed to some un-vented hot water cylinders (mains feed) we don't tend to have gas or oil fired direct tanks like you do, ours are either electric or indirectly heated from the boiler.

    Until recently we had vessel suitable for heating systems coloured red, while those suitable for domestic (hot & cold water) use were coloured white, grey or stainless steel.
    With the new rubber that is suitable for both uses I have seen them in red as well.

    As far as I am aware all our vessel are imported mainly from Europe.

    Hope that helps
  7. Last Plumber

    Last Plumber Plumber GSR Top Contributor!!

    As above, there are a lot of variations. In my neck of the woods I would say there are more sealed systems going in to replace open vented.

    Make/brands, there are many but no real preferences personally. All pretty much the same.
    Domestic properties over here, you'd Normally find a 10 Gallon F + E tank for heating systems and tanks for Cold water storage will vary.

    Does that help?
  8. TaylorBL

    TaylorBL New Member

    That's all really helpful, thanks for sharing so willingly.
    RPM had asked a question about the common size of expansion tanks over here. Water heaters run ~40-50 gallons and an expansion tank is 2.1 gallons (~$30-40 at retail).
  9. TaylorBL

    TaylorBL New Member

    That's all really helpful, thanks for sharing so willingly.
    RPM had asked a question about the common size of expansion tanks over here. Water heaters run ~40-50 gallons and an expansion tank is 2.1 gallons (~$30-40 at retail).
  10. TaylorBL

    TaylorBL New Member

    If anyone is still following, I'm curious to try and better pin down how often expansion tanks are used. For every water heater or boiler, will there always be an expansion tank? 50% of the time? 10% of the time?
  11. SimonG

    SimonG Trusted Plumber

    No. Stopped following.
    • Like Like x 1
  12. chris watkins

    chris watkins Plumber

    I would say that at least 95% of all heating vessels installed in this country form part of a boiler (combination or system) replacement of these are normally purchased from the boiler manufacturers.

    Not sure what % of hot water cylinders sold are un-vented & require a vessel, however those that are, are always supplied with a vessel by the cylinder manufacturer as a match pair.

    The market leading brand of unvented cylinder which I would guess amounts for 45% of sales are a bubble top & therefore do not require an expansion vessel. url&gclid=CJjUuffNzNECFYwQ0wodxiwIug
  13. chris watkins

    chris watkins Plumber

    duplicate post
    Last edited: Jan 18, 2017
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