Gas Supply Pipe Size Query

Discussion in 'Plumbing and Central Heating' started by Leon Westwood, 8 Nov 2021.

  1. Leon Westwood

    Leon Westwood

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    I currently have a Ferroli 38 HE Optimax Boiler that is 13 years old and would like replace it. My CO2 monitor activated due to low batteries, but it has caused me to reflect on the current boiler which also has a small water leak i have noticed.

    I have had a couple of quotes, but during my latest inspection the Gas Safe Installer queried the size of the gas main suggesting the 22mm Supply pipe was insufficient for the current boiler size.

    A vast majority on the gas main from the meter to the boiler is inaccessible on the basis it is buried under my extension. The short section either end is 22mm copper, but i am aware that the main pipe routed under the extension is yellow plastic, but I have no idea of the size. My estimation is that the yellow section of pipe is approximately 20 metres in length and would have been upgraded by the previous home owner who installed the boiler.

    Ideally, I would like to replace the boiler wfor one with a similar or greater DHW flow rate. The most recent installer suggested that was not possible due to the gas supply main size. None of the other quoters took any measurements of the pipe or asked about lengths or elbows.

    I am now left a little confused as where i stand. Is it possible to get a Gas Safe engineer to identify exacty what Size boiler I can install without being able to access the pipe?

    It is not an option to replace the main without digging up my extension sub floor, so I will have to pick a boiler that suits my current setup.

    The 3 visitors providing quotes all contacted me as a result of a online request from a boiler comparion site, so i have no previous knowledge of their expertise. My current boiler had a replacement fan a few years ago under warranty, but has had no issues concerning levels of gas supply.
     
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  3. muggles

    muggles

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    You'd be better off getting a reputable installer from either https://www.theheatinghub.co.uk/ or https://www.heatgeek.com/find-a-heat-geek/ than using some randomer from a comparison site.

    They are correct that your main is unlikely to be sufficient for your current boiler or a future replacement of similar size. Tell us the number of elbows you have and whether any other appliances are connected and we'll be able to give you a max boiler size on your existing pipe. Given the info you've provided so far my estimate would be 24kW max, less the power of any other connected appliances
     
  4. Harry Bloomfield

    Harry Bloomfield

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    But did he actually test the pressure under a full load?
     
  5. Leon Westwood

    Leon Westwood

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    I have no idea of the number of elbow other than the 2 nearest the boiler. The entirity of the rest of the pipe is buried under my extension or patio. Either end is 22mm copper, but i am aware that a vast majority is yellow plastic. From vague recollection the yellow pipe is similar in size to the 32mm drainage pipe.

    I have 2 x baths and 1 shower, so would like to keep the boiler the same size if possible. Would be reluctant to go smaller.
     
  6. Leon Westwood

    Leon Westwood

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    None have conducted any form of pressure test.
     
  7. ianmcd

    ianmcd

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    you cant have that Im afraid
     
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  8. Leon Westwood

    Leon Westwood

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    I have no other connected appliances.
     
  9. Leon Westwood

    Leon Westwood

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    Have the regulations changed? I dont understand how I have not had any pressure issues with my current boiler, but now i must go smaller.
     
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  11. Leon Westwood

    Leon Westwood

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    Apologies, I do not understand. Should there be no plastic pipe used on my installation?
     
  12. ianmcd

    ianmcd

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    you cant build anything over a plastic gas pipe
     
  13. muggles

    muggles

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    Regs haven't changed in recent memory, no - certainly not since your boiler was fitted. You're allowed a maximum of 1mBar drop in pressure between the meter and the boiler. This can be both measured and calculated. My calculator, assuming 6 elbows (two at the boiler, two underground, two at the meter) gives 0.83mBar drop on 22 metres of 22mm pipe with a 24kW boiler. A 28kW or higher exceeds the 1mBar limit and so requires a large pipe.
     
    Last edited: 8 Nov 2021
  14. Leon Westwood

    Leon Westwood

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    Is this the case for pipe between the meter and the appliance or just up to the meter. The pipe I am referring to is inbetween the meter and boiler.
     
  15. Harry Bloomfield

    Harry Bloomfield

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    How do you know that is the yellow plastic pipe?
     
  16. ianmcd

    ianmcd

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    doesnt matter before or after meter you simply can not do it
     
  17. Leon Westwood

    Leon Westwood

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    I don't to be fair. when we had the extentsion I just noticed the pipe passing through the footing channel. I looked similar to main replaced by national grid when the gas main was sunk deeper on my drive a few years later, so i just assumed it would the gas supply.

    The meter is at the front of the house and the supply boiler and and mains water supply come out of the concrete floor near to each other. I suppose it could be either water or gas.

    If that isn't the gas main then i am unsure where else the gas main could be and assume it is all under concrete. If the meter supply goes direct to the boiler then it is approximately 10 metres underneath a concrete subfloor with solid oak floor laid on top.

    The footings channels were inspected by the buildings inspector prior to being filled has I remember the builder and the inspector falling out over the fact that the extension footings needed to be considerably deeper than the original footings to the house. The pipe would have been viewable in that location.

    I dont know if the pipes are colour specific.
     
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