Running cold water pipe outside

Discussion in 'Plumbers' Talk' started by gpierce, Aug 11, 2017.

  1. gpierce

    gpierce Active Member

    I'm running some plumbing to the attached garage of my house for a washing machine, and have a choice of two routes - I can run the pipe inside the house but it's a less than ideal route and can't be hidden without quite a bit of work, but it's not the end of the world. I could also run the cold water supply on the outside of the house, which is a much shorter, simpler run.

    Now, I've already read about running cold water pipes outside, I know it's been asked before, and the general answer is no because of freezing in the winter, which makes sense, however it's really not an issue if I have the odd spell of a few days in winter when I can't use the washing machine, the advantage of the extra space in the kitchen would be worth the trade off in spades, so I don't really care so much if the pipe does freeze.

    The question is how susceptible are 15mm plastic pipes (and the associated push fittings) to bursting or cracking if the pipes freeze? I would expect an eventual leak with copper, but with plastic is there enough give to allow the expansion without cracking or bursting?

    My current plan if I ran outside would be;

    - Isolator inside prior to the run (which would be under the kitchen sink) so that if something did burst, I can at least isolate the supply without having to turn everything off, and then can repair when it suits me (although hopefully this doesn't need to be used).

    - Run the pipework in 15mm and add pipe insulation to help at least reduce the chance of freezing slightly.

    At some point when I redo the kitchen I'll do an inside run, so don't mind taking a bit of a risk (i.e. should be fine, but if we have an unusually cold winter then there could be problems) and because the outside run is so accessible, in the event of a repair it would be fairly straight forward.

    Probably a terrible idea, but any thoughts would be useful!
  2. Dave does Gas

    Dave does Gas Screwfix Select

    As you have said a method of isolation is crucial and as you plan an internal isolation valve is best.
    If you have no way of running the supply underground then the best pipe you can use would be MDPE, you have probably seen it around building sites camp sites etc.
    20mm will be suitable for you plus the fittings.
    If you choose to insulate the pipe dont use the bog standard insulation off a DIY merchants shelf as once it get wet it freezes and causes just as much of an issue as not insulating.
    There is waterproof insulation avaliable from most plumbers merchants. One good brand is Armaflex
    PhilSo and Pollowick like this.
  3. nigel willson

    nigel willson Screwfix Select

    Trace heating!!!
  4. Mr Rusty

    Mr Rusty Screwfix Select

    +1. After a burst a few years ago this sorts the problem completely

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