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Discuss Changing Back boiler for Combi in the Central Heating Forum area at UKPlumbersForums.co.uk.

  1. jbm

    jbm New Member

    Hi, I will be changing my trusty old Baxi back boiler for a combi in the next couple of weeks. I am competant to do the water side of the plumb and will employ someone to deal with gas and flue side.
    I am carrying out some preparations prior to proceeding and just checking before I chop a pipe or 2.
    The Radiators all run from a 15mm pipe with each spurred off in turn. The returns are congregated and appear to return to the boiler via a 22mm pipe. All pipes (very handily) go in front of the chosen location for the new boiler so diverting them will be an hour or so's work including a run off for the condensate (tank overflow)
    I intend flushing through the system prior to fitment of a new boiler. What are the best additives to push through the system to preserve the radiators etc?
    I have up until now removed the radiators 1 at a time annually and given them a good rinse with the garden hose but I would prefer to leave them be for a few years after the new system is fitted.
     
  2. Chalked

    Chalked Plumber GSR

    Needs a power flush.
    Why isn’t the gas guy involved in this choice, as he will be registering the the guarantee.
    Will need doing to qualiffor that.
     
  3. sammathias

    sammathias Plumber GSR

    Soooo...good luck if you can get someone to just run the gasline and commission the boiler.

    How do you know the old system will not leak under pressure?
    Needs 22mm flow and returns before teeing off for individual rads in 15mm
    Powerflush is generally needed so the warranty won't be void.
    Filter ftted
     
    • Like Like x 1
    • Agree Agree x 1
  4. Harvest Fields

    Harvest Fields Trusted Plumber GSR Top Contributor!!

    I would get a GSR to do the lot. But that’s just me.
     
    • Agree Agree x 1
  5. scott_d

    scott_d Plumber GSR Top Contributor!!

    1 pipe system?
    Do you plan to use the tank overflow as the condense waste?
     
  6. Rob Foster

    Rob Foster Top Contributor!!

    What you intend to do raises more questions than answers. Short term questions about system integrity and design. Long term questions about the guarantee for the new boiler, your house insurance remaining valid and its overall safety. I am sure on a
    job by little job basis you can attempt this but the sum of all its parts is a worrying prospect for your home and people living there. Good luck and keep us informed of your eventual choice of course of action
     
  7. jbm

    jbm New Member

    So, had plumber round this morning who pointed out several errors in the original fitment of the old system. Terrible mixture of 15 + 22mm pipework (22-15-22-15 etc etc). Seems to have been patched in with 'whatever was left over from other jobs', Poor overall installation. There's a rad return taped onto a gas pipe to 'hold it in place'. Complete renewal advised.
    Complete building was refurb'd about 25 years ago and going by other 'horrors' i have found in the basic fabric of the refurb. The DIY section of the heating is a no go, so whole house will be re-plumbed from scratch!
    Thanks for all the replies guys.
     
    • Like Like x 3
  8. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    I always recommend a repipe on an old back boiler at min a day flush depending on size
     
    • Like Like x 3
  9. Harvest Fields

    Harvest Fields Trusted Plumber GSR Top Contributor!!

    I learnt that early on.:eek::eek:
     
    • Like Like x 2
  10. sammathias

    sammathias Plumber GSR

    Even repipe the complete hot pipe too. It's quoted in.
     
  11. scott_d

    scott_d Plumber GSR Top Contributor!!

    Are you going to do the heating side?

     
  12. dan_the_plumber

    dan_the_plumber GSR

    There is a reason proper gas Safe plumbers do equivalent of 5 years in collage you know.
     
  13. Rob Foster

    Rob Foster Top Contributor!!

    Now I thought that gas safe engineers went to college and did not do collage with is what my wife does in her spare time sorry but I could not resist this
     
    • Funny Funny x 1
  14. dan_the_plumber

    dan_the_plumber GSR

    Bloody predictive text...lol
     
    • Funny Funny x 1
    • Winner Winner x 1
  15. jbm

    jbm New Member

    The mixture of pipe sizes uncovered looks a bit like a collage. Will need to try and post a photo. btw, the original fitment was by a 'national' gas company.
     
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