How to fit duct for Cooker hood extractor

Discussion in 'Electrics UK' started by lanham, 12 Jan 2022.

  1. lanham

    lanham

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    We have bought a Cooker Hood with facility for outside extraction. The 'plumber' has drilled a 115mm hole in the wall which is about 2m away from the hood. I can get 115mm flexible hose but is it OK to just push that through the hole in the wall and connect it to an outside vent? Another problem is that every external vent I can find is everything except 115mm. I am at a loss as to what to do. Any help or advice (except throwing the cooker hood away) would be greatly appreciated.

    Thanks

    Brian :cry:
     
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  3. flameport

    flameport

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    100mm duct or hose, and 100mm vent.
    Both of which will fit inside the 115mm hole.

    You may need an adaptor for the connection to the hood, some are supplied with them, others not.
     
  4. lanham

    lanham

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    Why didn't I think of using a smaller hose? DOH.

    Cheers
     
  5. oldbutnotdead

    oldbutnotdead

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    Do use rigid duct. The flexible will sag and collect grease and fluff. If you can get a slight downhill slope to outside, so much the better :)
     
  6. Harry Bloomfield

    Harry Bloomfield

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    Use rigid if possible, flexible corrugated will reduce the airflow drastically.
     
  7. lanham

    lanham

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    Yes, you are quite right. Glad I came back to this forum before ordering flex pipe. Will now go for rigid pipe, not that much more expensive either.

    Ta

    Brian
     
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  9. lanham

    lanham

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    Slight problem, I would like to get 115mm ducting but the most common size I have seen is 100mm. Does anyone think it would be a problem going from 115mm at the cooker hood end to 100mm which would then (via a 90 degree elbow) go out to the outside vent.
     
  10. Harry Bloomfield

    Harry Bloomfield

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    100mm rigid, will have much less reduction of flow than 115mm flexible - just put packing in the cap. So long as it is sealed, it will be fine.
     
  11. Sureitsoff?

    Sureitsoff?

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  12. oldbutnotdead

    oldbutnotdead

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    110mm waste pipe has served me well in the past :)
     
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  13. Taylortwocities

    Taylortwocities

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    You can get duct size adapters. Eg
    Click me

    bear in mind that the fan will be less efficient if you use a smaller outlet than the extractor requires.
     
  14. lanham

    lanham

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    Thanks to everyone. I am getting some 150mm rigid pipe, short piece of 100mm pipe, a 90 degree bend and an adapter to go from 150mm to 100mm to go through the wall.
     
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