Gas pipe

Hi ...having a new valiant boiler being fitted In 3 weeks which requires 22 mm gas supply ,...I have 18 mm all the way to boiler at moment .....can the 18 mm be cut 3 metres away from boiler and upgraded to 22 mm to increase supply has my floors can not come up ...I have mounted wall gas pipe behind kitchen unit at the moment which can be altered if necessary


  • Mister_G
    Mister_G Posts: 1,922
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    Most modern gas boilers do require a 22mm gas pipe to cope with the increased flows required.  It is very unlikely that increasing the last 3m to 22mm will suffice.

    Your RGI who is doing the install will be the best person to ask.  BTW the existing pipe will probably be 15mm copper or 1/2" iron. 
  • matelodave
    matelodave Posts: 8,569
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    Making the last 3 metres 22mm wont improve the flow or volume of gas that comes through the remaining narrower pipe - the whole length will need to be upgraded back to the meter
    Never under estimate the power of stupid people in large numbers
  • tim_p
    tim_p Posts: 678
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    We had a new Vaillant boiler fitted a couple of years ago and there was initially concern it might need a 22mm pipe instead of the 15mm already installed.  Got a second opinion and it’s fine with the 15mm. Had it been a combi boiler then it would have needed the 22mm. 
  • 22mm from the meter required I am afraid.
    Some boilers have a 15mm connection for gas but usually still require 22mm up to 1m from the connection point.

    Upgrading the last 3 metres will not suffice and should your RGI do that, they should be questioned.
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