22mm Gas Pip Regulation for Combi Boilers

Discussion in 'Plumbers' Talk' started by GC129, Jan 4, 2023.

  1. GC129

    GC129 Member

    Heya, I am in the process of getting a new boiler, and have had two different companies say different things about the regs for gas pipe size into the boiler.

    First company have said it needs to be 22mm to meet new regulations. The second company have said that has long as the flow rate is sufficient (once they have installed and tested it), the current 15mm (I think?) going into it will be fine (there is 22mm into the house, but where that ends we do not yet know, it could be under the floor below the boiler).

    Its a small flat (9 radiators) and no other gas appliances. The second company have suggested a glow worm boiler that requires less gas flow than other models.

    Whilst I am keen not to have to rip up things to lay in a new gas pipe, I don't want this to cause me problems down the line with getting gas safe certificates / selling the property on.

    Any advice greatly appreciated!

  2. dcox

    dcox Screwfix Select

    As a rule of thumb, most set ups need at least a 22mm gas pipe unless it’s close to the meter but that’s purely to ensure an adequate supply without more than a small difference in working pressure between the meter and the boiler.

    The second supplier is how I’d approach it. Try it with the existing pipework but accept that it may well have to be upgraded if the readings don’t come up to scratch. Obviously this would be at the customers’ cost.
    Deleted member 246321 likes this.
  3. candoabitofmoststuff

    candoabitofmoststuff Screwfix Select

    I'm not a plumber, only DIY, but I had my boiler replaced 18 months ago and got cluded up on this kind of thing at the time...
    You haven't said what type of boiler... If it's a combi then I'd be surprised if 15mm is sufficient.
    If it's a heat only then 15 might be OK.
    I'm saying that from a "what might work" perspective... not a "regulations" perspective!

  4. Tilt

    Tilt Screwfix Select

    Mine was fine using the existing 15mm, but literally few feet away from each other.

    NB this was a Heat Only though, and a Combi could well be a different matter.
  5. Tilt

    Tilt Screwfix Select

    It's in the title bud.........
  6. Bob Rathbone

    Bob Rathbone Screwfix Select

    It is very likely that the 15mm pipe will supply enough gas for the central heating as it's a small installation. With a combi it is the hot water that eats the gas, this is where the issue of pipe size may arise. Regulations do not simply state a pipe size as this will be dependent on the length of run and the gas demand.
    Cliff Rees likes this.
  7. Tilt

    Tilt Screwfix Select

    What is your current boiler type ?????
  8. candoabitofmoststuff

    candoabitofmoststuff Screwfix Select

  9. GC129

    GC129 Member

    Thanks for the all the advice everyone- much appreciated.

    @Tilt - current boiler is a valiant ecotec pro 28. proposed replacement is a Glow worm Energy 25c

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