32mm mdpe or 25mm

Discussion in 'Plumbing and Central Heating' started by xdrive, 27 Apr 2020.

  1. xdrive

    xdrive

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    Hi.

    Replacing lead pipe. Having stopcock on road renewed. Neighbors say flow is good.

    Do I use 32mm or 25mm? House has been extended with dormers. 3 floors 2 bathrooms.

    I've dug trench between 700-750 deep. Do I insulate pipe or duct it? Will lie on subfloor when inside.

    Cheers
     
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  3. dilalio

    dilalio

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    Depends what stopcock/meter is being fitted... Usually no point in using 35 unless supply is around that size. 25mm usually and bed it in pea shingle at the bottom of the trench. Might want to lag it in the house but mdpe doesn't really suffer from condensation that other pipe materials can do.
     
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  4. Madrab

    Madrab

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    Rarely would I contradict the pro's on here, especially @dilalio - ;) - but if the mains pressure and flow can sustain it then no reason not to go to 32mm to maximise your supply.

    If you are having the lead mains replaced though, you really should be getting a note of what the mains flow and pressure and the pipe size would be. Specifically to answer your question.
     
  5. JohnD

    JohnD

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    That's how I look at it.

    The cost difference in pipe is not much, and the effort is the same.

    The big stopcock is dearer, though.
     
  6. xdrive

    xdrive

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    That's what's stopping me. Is there a way around this ?

    What if I get 32 to 32 stop cock then use reducer from 32 to 28?

    Would you use 22 or 28 copper?

    Does the water company have to attach blue pipe coming into to my side from road stopcock? If it can be done by plumber then will let water company install them then see what they have used and get same size.
     
  7. JohnD

    JohnD

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    I'm not a plumber.

    When I replaced lead with plastic, I used the large size and took a 22mm cold and a 22mm for the hot off it, with the idea that neither would steal flow from the other, even if you're running two baths or showers.

    Dilalio will have done lots so knows better (hope he isn't offended by DIYers)
     
  8. xdrive

    xdrive

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    If I use similar set up but with 25mm mdpe (bore size 22mm) to 22mm copper hot and cold would I be unable to run 2 showers at same time from boiler?
     
  9. JohnD

    JohnD

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    Don't know. I did it by eye. There is a way of calculating it.

    Flow was fantastic afterwards.
     
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  11. Madrab

    Madrab

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    Unfortunately that isn't dictated by the size of the mains supply unless you are using an unvented cylinder. If it's a combi boiler, it will probably struggle no matter what size of pipe you use I'm afraid. It can be designed to work but it needs tight control on the shower types and fittings to regulate the flow from each.

    TBH - the price difference between a 32mm stop tap and a 25mm stop tap isn't that much in the grand scheme of things IMO.
     
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  12. xdrive

    xdrive

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    What size stopcock did you use? 32 to 22m?
     
  13. JohnD

    JohnD

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    Two @ 22 indoors.

    Outside, the water meter had its own stopcock
     
  14. Madrab

    Madrab

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    I'll get me coat!! :whistle:
     
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  15. xdrive

    xdrive

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    As the mdpe comes in to the property it is around 550-600mm. It will then lay on subfloor for 7metres and finally come up in kitchen.

    Do I need to use lagging/ducting on of what sort?

    Also I would like a garden tap. Is it best to take of the mdpe? Cheers
     
  16. Madrab

    Madrab

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    Have as look at this thread, the post from @Hugh Jaleak, if anything as @dilalio suggest, you can use a pea shigles or sand for the trench. The insuduct is an excellent way to bring the pipe out of the ground and into the house.
     
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  17. Hugh Jaleak

    Hugh Jaleak

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