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Replacing traditional central heating with combi boiler - is it easy?

I have a traditional gas fired central heating / hot water system, with a header tank in the attic, boiler in the kitchen, and hot water cylinder in the first-floor bathroom.

The cylinder takes up a lot of space in the bathroom, so I want to get rid of it and install a combi boiler instead (in which case a cylinder won't be necessary). Is it just a simple case of swapping the old traditional boiler in the kitchen with the new combi boiler, and removing both the cylinder from the bathroom and header tank from the attic?

Are there any other alternative solutions other than a combi boiler I could consider (as long as I can get rid of the huge cylinder in the bathroom!)


  • olly300
    olly300 Posts: 14,736 Forumite
    First Post First Anniversary Combo Breaker
    How many bathrooms do you have?

    As combi boilers aren't recommended for houses with more than one bathroom.
    I'm not cynical I'm realistic :p

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  • david29dpo
    david29dpo Posts: 3,748 Forumite
    First Post First Anniversary Combo Breaker
    If you know what you doing its fairly easy. I intend to do this in the near future. Luckily i have a cold & hot water pipe very near the boiler (new boiler needs a cold feed to the DHW & filling loop) The feed & return are already there! Remove the header tanks, remove the pump and 2/3 port valve. The new boiler will also need a drain, similar to a washing machine drain outlet. Remember to get the gas man to connect it for you!
  • jimbugalee
    olly300 wrote: »
    How many bathrooms do you have?

    As combi boilers aren't recommended for houses with more than one bathroom.

    We currently have two bathrooms and can have all taps running, in kitchen too and there's no problem but we have the most powerful Bosch boiler. We made sure it would definitely cope! I think if you buy one too small/under powered? (not sure how it's measured) then you may run into problems.

    We just replaced our gas CH heating system with a combi boiler and removing the copper tank. I get slightly confused as we also had to install new pipework for new radiators and rooms etc. I am assuming you may not have to do this?

    Our main problem was the new regulations meant that some of the pipework had to be a bigger diameter and couldn't run in the original place (under floor boards).

    I think you would have to consult a professional before going ahead. Not necessarily to say it will be complicated but I would check.
  • ormus
    ormus Posts: 42,714 Forumite
    we did this 3 yrs ago. the new boiler was resited too into a bedroom cupboard.
    there were no major problems. the are a few rules about tail pipes/diameters but no big deal.
    no large scale pipe size changes were needed. simply connected to the nearest point/s in the system. which was under the floor about 2 feet from the cupboard.
    a new inlet feed was needed, but that was easy enough. about ten foot long to the bathroom.
    Get some gorm.
  • ahfh1
    ahfh1 Posts: 193 Forumite
    olly300 wrote: »
    How many bathrooms do you have?

    As combi boilers aren't recommended for houses with more than one bathroom.

    There is 1 bathroom at the moment, so a combi should be sufficient.

    The reason why I aslo asked for alternatives to a combi is because I may build an extension to the house in a 2 years time which will have another bathroom. So I want to future proof the heating system for the extra bathroom when the time comes, yet at the same time get rid of the huge cylinder in the bathroom.
  • DVardysShadow
    DVardysShadow Posts: 18,949 Forumite
    Having gone from a house with a well designed and installed fully pumped conventional system to another with gravity hot water to another with a combi boiler, I strongly prefer the fully pumped system over the others. The hot water cylinder with both the fully pumped and gravity systems made for a good airing cupboard and drying room. The combi is good for house heating - it is marginally quicker than the fully pumped for heating from cold, but nothing like as good for maintaining house temperature.

    Given a blank sheet, i would go for fully pumped every time
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