cutting a hole in a cast iron soil pipe

Discussion in 'UK DIY' started by Steve, Aug 10, 2003.

  1. Steve

    Steve Guest


    In order to plumb-in a washing machine, I need to connect to the old cast
    iron soil pipe to carry away the waste. (The pipe is just over 4 1/4"

    Can anyone recommend a good way to cut the hole in the pipe, to connect a
    boss ?

    I've seen an old post where someone recommended drilling a ring of closely
    spaced holes and then joining the holes so the disc can be removed. But I
    don't see how you'd be able to drill the holes closest to the wall.

    Whatever the method, I don't want to risk cracking the pipe - presumably old
    cast iron is fairly brittle.

    Many thanks

    Steve, Aug 10, 2003
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  2. Steve

    BigWallop Guest

    If you can get hold of a fine toothed hole saw, one which looks like a
    hacksaw blade, of the size you need it will make life a bit easier. But no
    matter what method you are thinking of using, you'll need some kind of
    cooling liquid squirted on the point you're drilling to save the drill bit
    and to reduce the possibility of the pipe heating around the drill point and
    BigWallop, Aug 10, 2003
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  3. have you considered just cutting out a section of the iron pipe (with an
    angle grinder) and slipping a length of plastic pipe in its place?

    John Stumbles
    Experiments to demonstrate the existence of Sod's Law by dropping
    slices of buttered toast all failed. That's Sod's Law.
    John Stumbles, Aug 10, 2003
  4. Steve

    dg Guest

    If you can't get hold of a suitable steel hole cutter, then cut the
    pipe and fit a plastic connector with the facility to fit a boss. Most
    manufactures make a connector/adaptor fitting

    dg, Aug 10, 2003
  5. Steve

    Steve Guest

    have you considered just cutting out a section of the iron pipe (with anboss.

    Thanks for the suggestions. But if I cut the soil pipe, it will mean the
    (not inconsiderable) weight of the upper part isn't supported by the lower
    part; this will put a lot of stress on the 2 higher supports and on the
    outlet from the upstairs toilet. Isn't this a problem ?

    Steve, Aug 10, 2003
  6. Steve

    fred Guest

    Not the cheapest, but suggest you cut a hole with a hole saw (57mm) and
    use a strap on boss. The boss has a flange which fits inside the hole &
    makes the whole thing a bit less hit & miss. Add sanitary silicone around
    the flange before fixing. Boss will accept rubber or solvent adaptors.
    Rubber adaptors look insecure, but solvent leaves you without an option to
    dismantle. A solvent stub mated to a pushfit pipe makes the job a bit more

    List of bits, prices and codes are for

    57mm hole saw code 7799 £6.11 + vat
    Large Arbor code 7801 £8.40 + vat
    Strap on boss 110mm grey code 13002 £1.61 + vat
    Adaptor rubber 32mm code 11191 or 40mm code 11192 cost about 90p
    Solvent & other adaptors on site, post is free

    fred, Aug 10, 2003
  7. If it's as I imagine I think the outlet from the upstairs wc connection will
    help support the rest of the stack, but it should have proper supports
    anyway. You could always add some more if you think fit (using steel or iron
    brackets of course, not plastic).

    It's brittle to the extent that if you wack it with a hammer it may crack.
    Sod's law dictates that it will resolutely refuse to do so if you want it to
    and do so too easily if you don't :)

    When I've cut a pipe that was in a corner, using a 4" grinder, I cut halfway
    through the pipe at 2 points about a foot apart and sliced lengthways to
    remove a sort of rectangular section, then I could get the grinder in to cut
    the rest of the way through to the back of the pipe. USE A MASK: the dust
    and other stuff that comes of grinding through a soil pipe is outlawed for
    use in combat under the Geneva Convention.
    John Stumbles, Aug 10, 2003
  8. Steve

    Steve Guest

    Many thanks to all who replied.

    I didn't realise that you can get hole-saws that can be used on cast iron.
    As they are available, I'm going to cut the hole directly into the cast
    iron pipe.

    Steve, Aug 11, 2003
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