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Discuss Boiler change needed for loft conversion - problem with gas supply for combi boiler in the Central Heating Forum area at

  1. Bob Smith

    Bob Smith New Member

    We're hoping to have a loft conversion done soon, in what is currently a three bed mid-terraced house - we are adding a new bedroom in the loft with en-suite shower and toilet.

    Currently we have a traditional heating system with boiler in the kitchen, fed by gas pipes under the house, hot water tank upstairs and a cold water tank / condensing tank pair up in the loft.

    Our initial plan was to replace this with a single combi boiler, and we got British Gas to come and do this before the loft work began. However, there was a problem with the gas supply - the current supply is not sufficient for a combi boiler, and because of the configuration of the house (with gas supply at the front and boiler at the back), British Gas said it was impossible for them to safely get enough gas through for the combi boiler. It would require routing the pipe up to the first floor, under the laminate flooring all the way to the middle of the house, then back down to the kitchen (under the bathroom) and along to the boiler at the back. They felt that this arrangement involved too many kinks, and even with 1 inch piping they couldn't guarantee that there would be sufficient gas supply for a combi boiler.

    They therefore suggested that the best option was to retain a traditional system, with a slightly bigger traditional boiler, and get the loft conversion people to relocate the cold water tank into a corner of the eaves of the loft, so that it's out of the way once the new bedroom is built up there.

    The builder and his plumber, however, are reluctant to go down this route, they think it's too much work to move that cold water tank, and that it would require pumps and other complications. Their plumber came to look, and thought that the risk of installing a combi boiler had been exaggerated by British Gas, and that it would be fine to route it via the first floor as suggested.

    I would appreciate any independent advice on this. Is it really difficult to relocate a cold water tank into the corner while doing loft conversion work, and also what are the likely risks with using a combi boiler with a complicated multi-kink gas pipe serving it? Thanks.
  2. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Couldn't they go externally with the gas pipe

    Do you know what kw the new combi boiler would be ?
  3. oz-plumber

    oz-plumber Plumber

    Sounds like you are getting 'jibbed'.

    Ask the builder what he has allowed for the works and then ask him what the works requested by you would cost.
    As for relocating the tanks and pumping the system, ask them why?
    Doesn't sound too hard to me.
    It could be that the builder hasn't allowed for the works that you require / request.

    Running a gas line can be difficult at times, but it's for your convenience.
    As for a BG saying what they told you says it all.
    They want to do the job their way - not your way.
  4. jtsplumbing

    jtsplumbing Plumber GSR

    What about replacing cylinder & Boiler for a pressurised system (Magaflow) that way you would get rid of tanks in roof and it would give you good water supply to top floor or do you have problem with space / water supply
  5. sammathias

    sammathias GSR

    Say you where installing a 28kw boiler. You could literally get away with a 45meter gas line straight with 28mm pipe. Taking into account bends and fittings id say even a 30meter gasline would be sufficient. Think britsh gas are mugging
  6. sammathias

    sammathias GSR

    As shaun said...why not go external with gas pipe?
  7. Bob Smith

    Bob Smith New Member

    Hi all - yes, we considered going external, but we're in a mid-terraced house, so unless we try to route the pipe all the way around the neighbour's house as well, that's a non-starter :)

    As it happens, I spoke to another neighbour with an identical house to ours yesterday, and she said they switched their trad boiler for a 30kW Worcester boiler recently, with the existing gas supply, and have had no problems. They haven't used it through the winter yet though. I guess the danger with that is if the supply does prove insufficient at any point, the boiler's warranty is invalidated.
  8. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    You have another option but you would see the pipe on the front of your house

    Go external on the front and up into the soffits and to the boiler in the loft (if you could and acceptable to you)
  9. Moffski72

    Moffski72 Moffski72 GSR

    Why even get BG involved? They will be 50% more expensive than any independent heating engineer, whatever you have to do with your gas supply. Is your builders' plumber not gas safe registered? Why not ask him to fit your boiler etc as an extra part of the works?
  10. Bob Smith

    Bob Smith New Member

    We just wanted to get someone independent involved, as the work is separate from the loft work, and BG have a good reputation in this area. Maybe that was a mistake though. It worries me that they think it's not doable, whereas the builder's plumber thinks it is doable. The builder's plumber is prepared to try fitting the boiler and see if there is enough supply, then route the pipes through the house if he finds there isn't enough supply. Sounds a bit hit and miss to me, and not sure if it invalidates the boiler warranty if it turns out tehre isn't enough supply, but maybe this is going to be the best option to pick.
  11. AWheating

    AWheating Trusted Plumber GSR

    Your existing gas supply will definitely be to small 99.9% of the time. Your neighbors have probably either been lucky or more likely had a badly fitted boiler. I can't imagine that the gas route suggested by BG would not work, just needs sizing correctly. What's your water mains pressure and flow rate like?
  12. Moffski72

    Moffski72 Moffski72 GSR

    Whoever you get to do it needs to size the gas supply according to the load on it. Don't let BG dictate what you should have in your property to fit in with their profit margins, YOU'RE the customer and if you know what you want (?) then it's whoever is fitting its' responsibility to do it so that it will supply the right amount of gas under full load. A decent combi will give you a great shower, even if someone does decide to do the washing up at the same time...although not many will run two showers simultaneously.
    A pressurised hot water cylinder is only as good as the incoming cold water supply to it, but in most cases will run two showers together, so if that is going to happen often, that's probably the way to go. You would still get rid of the loft tanks by fitting a pressurised (system) boiler rather than the vented one (with the little tank in the loft) that you have now. G'luk.
  13. sammathias

    sammathias GSR

    Neighbours boiler is probably undergassed and not running efficently. As for the plumber. He should be able to work out the correct pipe sizing for the gas pipe, if hes just going to fit it and hope its getting sufficent gas thats not very professional.
  14. Bob Smith

    Bob Smith New Member

    So, just to summarise the thoughts above:

    * We should not copy the neighbour's approach of trying to connect the combi boiler to the existing pipe, as we might be setting ourselves up for problems later on, if the boiler requires a heavier gas use during time when the hobs are on etc. Note that the builder's plumber has also suggested this approach - to connect it up, see how it goes, and only lay new pipes if necessary.

    * Routing a new thicker pipe to the kitchen via the first floor may be the best approach. The builder's plumber has quoted about 5 grand for this work. I'm tempted to get BG to quote for the work too, and maybe another plumber.

    * BG's suggested solution, incorporating a relocated cold water tank into the loft designs, may be worth considering but both the builder and his plumber have said this is a bad solution. Not sure if it's worth pressuring them to do this, or just go with the routing the pipes work.

    Does this seem like a reasonable approach?
  15. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    5 grand for what exactly just the gas pipe ?
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