Hole size for 15mm Copper Pipe Through Timber Floor

Discussion in 'Plumbers' Talk' started by Big Red Ant, Mar 8, 2017.

  1. Big Red Ant

    Big Red Ant New Member


    Hopefully a nice easy one.

    I am moving a radiator from one wall to another one. What size hole should I be drilling for the pipe to pass up from under the floor to the radiator? I can't look at the old holes because the floorboards have been notched then put in place after the plumbing first fix when the house was built. I just want a nice tidy hole that is not too big or small. 15mm is the obvious answer but no room for expansion if some is needed.

    Thank in advance.
  2. Dr Bodgit

    Dr Bodgit Well-Known Member

    Depends on the size of the drill bits you have to hand....around 18mm I'd say.
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  3. andy48

    andy48 Active Member

    I'd agree with 18mm, but you have to make sure the centre of the hole is exactly (left to right and front to back) under the centre of the valve to which the pipe will be connected. 1.5mm in any one direction off centre doesn't allow for much adjustment.
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  4. nigel willson

    nigel willson Well-Known Member

    Don't make 15 mm bits far as I know , 16mm nearest but 18 gives bit of leyway
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  5. KIAB

    KIAB Well-Known Member

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  6. Mike83

    Mike83 Well-Known Member

    The bigger the hole the more play the pipe will have. This will help to keep the pipes straight, left to right and front to back. It will also help when the radiator needs to come off the wall at some point.
    It can be a pain when the valve won't slip off the tail when removing a rad.
    I'd go 18-20mm if the floorboards are hidden.
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  7. Big Red Ant

    Big Red Ant New Member

    Hi All

    thanks for your help. Think I will go with Mike83 and make a 20mm hole as floorboards are hidden by carpet and gives me some room for movement as I'm not a plumber so I expect I will need some.

    Much appreciated.
  8. Dr Bodgit

    Dr Bodgit Well-Known Member

    I imagine that ones the pipes are in place, you could fill around the pipe where it comes through the floorboard with caulk or silicone of some sort. Otherwise you'll get dirt coming through and staining the carpet. Or use a bit of pipe insulation cut to size, or pipe lagging etc.
  9. durrans

    durrans New Member

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