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 on a 1 pipe system in the Central Heating Forum area at

  1. KingDoey

    KingDoey Plumber GSR

    As above will it work?

    Doing a combi conversion and lifted some boards under radiator to alter some pipework and discovered the heating circuit is a one pipe system!

    I have only ever removed this type of system never connected onto it.

    I know the it won't be as efficient and I am going to recommend a re pipe. However will it work properly should they choose to ignore my advice?

    many thanks
  2. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    I will work but some manufacturers won't warrenty the boiler, also as you have said not very efficient
  3. KingDoey

    KingDoey Plumber GSR

    Cheers Shaun its a Worcester so will give them a ring and find out
  4. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Worcester are fine with it the only other one I know is villant
    • Like Like x 1
  5. KingDoey

    KingDoey Plumber GSR

    Goody gumdrops
  6. townfanjon

    townfanjon Trusted Plumber GSR

    Thousands of one -pipe systems out there , if you hadnt lifted the boards you wouldnt have known
  7. Chalked

    Chalked Plumber GSR

    Yet it will work, but my advice would be, go round and check all rads work before you start.
    I've been caught out before, by the customer that says " that used to work before you changed the boiler"! Only to take a board up to find it's been taken 20feet from the one pipe loop.
    As long as no one has adapted the system, all should be fine. Obviously, power flush before new install.
    Last edited: Jan 7, 2017
  8. KingDoey

    KingDoey Plumber GSR

    Cheers for the advice. Yeah system was powerflushed. Halfway through the job now so no going back. Customer is pretty sound though so shouldnt be any issues like that. Like i say we defo recommend it gets repiped
  9. johnf

    johnf Active Member

    Just make sure that the return temperature isn't too low. Some manufacturers say that the return to the boiler must be above 40 degrees to prevent the heat exchanger rotting out. If this is the case fit a bypass/three port mixing valve between the flow and return.
    You can't really powerflush a one pipe system very well as it wont go through the radiators without some persuasion. As said above it needs to be repiped.
    • Like Like x 1
  10. Mattyg123

    Mattyg123 New Member

    Did the system work fine?
  11. KingDoey

    KingDoey Plumber GSR

    Flew round. Worked like a dream
Similar Threads - Combi pipe system Forum Date
Combi Boiler for Heat Only Plumbing Forum Yesterday at 7:50 PM
Baxi 80 HE Instant combi hot water issues Gas Safe Registered Plumbers Only Tuesday at 10:39 PM