Posting a message to the forum will remove the above advertisement
  1. Checkout our Plumbers Insurance area - heavily discounted Public Liability Insurance and Van Insurance specifically designed for plumbers.

Discuss Combi Boiler Fitted-Is This Right ?? 22m to 15m supply in the Central Heating Forum area at

Thread Status:
Not open for further replies.
  1. saxonscoundrel

    saxonscoundrel Guest

    Hi-new here, we just got a combi boiler fitted.

    I was told we need 22mm supply and old supply was 15mm which ran under concrete floor.Was told it was easier to run gas supply the the length of house to the back with 22mm copper pipe.

    The current set up was 22mm from the meter box into the house under floorboarded dining room,which then reverts to 15mm somewhere between the dining room and living room[which is solid floor]

    This seems fine but just before it enters the house there the 22mm pipe then reverts back to 15mm and stays 15mm roughly the metre or so to the boiler.

    Looking at the manual [its a valliant eco tec] it says it need a 15mm supply,and also states

    "Exisiting meter should be checked to ensure it is capable of passing the rate of gas supply required.Pipework from the meter to the boiler must be of an adequate size.Do not use pipes of a smaller size than the boiler gas connection [15mm]"

    I`m no expert but this makes me wonder why run 22mm pipe round the house?? wouldn`t it have been easier to simply use the existing 15mm supply that was already in the correct position used with the older boiler???
  2. Blake

    Blake Plumber GSR

    The new combi boiler will require sufficient gas flow in order to operate correctly. Yes the final connection may be 15mm, but you still need to ensure sufficient gas flow.

    Depending on the length of the gas pipe, it may need to be 28mm, then 22mm and finally connecting at the boiler via a 15mm fitting.

    It's never ideal having pipes in concrete floor especially if you dont know how or if they are wrapped or protected.

    Installing a new gas run on the outside of the house is common practice.

    Should you not have questioned your installer before the new boiler was fitted rather than after?

    Anyway, it all sounds fine to me. :)
    Last edited: Apr 24, 2010
  3. oldplumber

    oldplumber Guest

    I think your final paragraph explains everything and if you have employed a registered gas engineer then you should be happy to accept their work is to a satisfactory standard, or you can ask gas safe to check the work if you have reason to believe there is a problem. By reading and querying the installation manual you have ventured into the unknown and as ever a little knowledge is dangerous:rolleyes: If your unhappy with things still, register on a 4 year training course at your local college and youll be able to discuss any problems on a level playing field with your rgi:)
  4. prs1

    prs1 Guest

    Well said!
  5. Billy Bob Bob

    Billy Bob Bob Guest

    have to agree,well said:D
  6. Blackcatgas

    Blackcatgas Plumber GSR

    The last 837 I installed needed the first 6m in 28mm pipe, then 22 the rest of the way.
  7. fuzzy

    fuzzy Guest

    Gas i relatively low pressure, there is alot of friction loss when running through pipes. Therefore, to garantee as you say the regs in respect of supplying enough gas to the appliance it is common to upsize the pipework.
    Id say the fitter has done you a good service, many would just put up with an undersized previous old pipe where u have a new at worse oversized pipe
  8. saxonscoundrel

    saxonscoundrel Guest

    Thanks for the replies,and i agree,a little knowledge can be dangerous.

    I didn`t have a problem with it,just wanted to hear what was common practice really,and i`m grateful for everyone who took the time to respond.

    Its all working great and is much better than the worn out thing it replaced so its all good!!!!
  9. Robtheplumb

    Robtheplumb Guest

    And none of us have heard that one before!
  10. Puddle

    Puddle Plumber

    Hopefully it will be ,helped by the correct working pressures at the appliance due to the correct pipe sizing by your engineer
    [​IMG] [​IMG]
Similar Threads - Combi Boiler Fitted Forum Date
Combi Boiler for Heat Only Plumbing Forum Yesterday at 7:50 PM
Old combi is dead - need recommendations for a system boiler and unvented tank Central Heating Forum Jan 6, 2018
Thread Status:
Not open for further replies.