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House refurb - changing gravity fed system to combi

Discussion in 'Plumbing and Central Heating' started by MarcoM, 11 Feb 2019.

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  1. MarcoM

    MarcoM

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    Hello we are buying a house and the current setup is tank in the loft and electric heater for the hot water. Central heating is gas.
    The setup is the original one from the 1980s.

    We would like to update the system to a COMBI boiler and I was wondering whether we should also get the existing central heating pipes changed. I read somewhere that when a system gets switched to Combi sometimes the existing old pipework can leak and it makes sense to replace this too. We are replacing all the radiators anyway.

    any thoughts would be appreciated.

    Regards,
     
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  3. bernardgreen

    bernardgreen

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    Is a combi the best option for your new house ? A hot water cylinder and a non combi ( but condensing boiler ) might be the better option as regards hot water supply.
     
  4. oldbuffer

    oldbuffer

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    As a suggestion, get the installer to pressure test the system to, say, 3.5 bar. This is half a bar over the maximum it should face with a combi, even in fault circumstances. If it can take an hour, or longer if possible, without losing pressure, then it should be OK in normal use. Replacing the pipework can be quite disruptive, particularly if you have tiled or laminated floors.

    As bernardgreen has asked, is a combi the best solution for you? Have you had the water main pressure and flow rates tested to see if they are adequate for a combi? How many bathrooms? most combi's are not that happy with more than one hot water outlet being used at a time, although there are exceptions.
     
  5. MarcoM

    MarcoM

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    many thanks for the replies.
    we are not really happy having a tank in the loft that
    is one of the main reasons for having a combi system.
     
  6. bernardgreen

    bernardgreen

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    You don't need a cold water tank in the loft if you have a non-vented hot water cylinder. The radiator system can be pressurised and that removes the need for an F&E ( feed and expansion ) tank in the loft.

    quite a few home owners and tenants are not that happy with the limitied flow of hot water from a combi boiler.

    .
     
  7. JohnD

    JohnD

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    those are not the only two alternatives.

    How many bath/shower rooms are there?
     
  8. MarcoM

    MarcoM

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    two bathrooms two of us in the house
     
  9. MarcoM

    MarcoM

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    if the system is pressurized would it mean that old pipes from the 80s install are likely
    to be a problem?
     
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  11. fixitflav

    fixitflav

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    You most likely have 2 tanks in the loft, a cold water storage tank and a smaller F/E tank for the heating. Do you want to get rid of both?
     
  12. MarcoM

    MarcoM

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    yes that is a non negotiable with the other half...
     
  13. HERTS P&D

    HERTS P&D

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    Does she/he spend that much time in the loft?

    Andy
     
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  14. MarcoM

    MarcoM

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    she worries about leaks whilst being away. one of our friends had a massive flood due to tank burst.
     
  15. HERTS P&D

    HERTS P&D

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    Always turn the mains off when you go away.

    Andy
     
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  16. MarcoM

    MarcoM

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    could i keep the original heating pipework with this combination or will it have higher pressure than the pipes can currently take?
     
  17. bernardgreen

    bernardgreen

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    Hard to say, I have known people who did have leaks when they converted to a pressurised system from a non pressurised ( tank in loft ) system. Others didn't have any problems with leaks.
     
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