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Building Regulations and Standards: Pipes in Screed

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1 to 14 of 14

  1.  
  1.  
    We need to run hot and cold in screed, finished floor will be tiles

    What are the regs. on running plastic pipe in the screed in one straight run with no joints underground?

    This is replacing a previous leaking copper pipe

    Thanks in advance
  2.  
    I think best practice may be inside a flexible conduit so that it can be pulled out and replace in future. there may be other reasons too. They make flexible conduit to suit different size pipes.
  3.  
    Like so. UFH pipes obvs not in conduit, Hot & Cold to handbasin in conduit.
      pipes in screed.jpg
  4.  
    Okay great

    I wonder if there is a minimum depth within the screed or can we tile over...
    • CommentAuthorrevor
    • CommentTimeApr 28th 2022
     
    I think the regs are if you are running cold water to a sink, not sure if it is just a kitchen sink, but i believe it is illegal to run a cold pipe next to a pipe that can heat up the cold water so that will be a problem with next to UFH or a hot water pipe. When I did my build the cold came in a duct in the slab, and hot went in a duct in the insulation that wat under the UFH. Can see that you cannot do that. Important you get it right as I think you can be prosecuted if you run cold next to hot but don't quote me.
  6.  
    The UFH in that pic is from a heat pump so less than 35 degrees C, usually less than that. I can't see it being a problem.
    The hot & cold supplies do diverge a bit on the way! (the cold goes via the toilet cistern)
    the depth here is at least 50mm because there is a brick floor as the surface, probably more like 60 - 70mm below the surface with the screed.
    •  
      CommentAuthorfostertom
    • CommentTimeApr 28th 2022
     
    I know it feels worrying but if UFH pipes can go unconduited, what's the rationale for H&C? Actually they just don't leak (do they?) and do we really want to pull them out one day? I wouln't rely on conduit as Hot insulation.
  8.  
    Most of the alpex pipe sold here is pre-insulated (for not much more than plain alpex pipe) which whilst you would not be able to replace the pipe as a pull through it would mitigate the warming of the cold water and retain the heat from the DHW pipe. It might make sense to use insulated or conduit pipe for the DHW pipe as this will be subject to more and more frequent thermal expansion and contraction then the UFH pipe and so subject to more abrasion.
    •  
      CommentAuthordjh
    • CommentTimeApr 28th 2022
     
    Posted By: fostertomI know it feels worrying but if UFH pipes can go unconduited, what's the rationale for H&C? Actually they just don't leak (do they?) and do we really want to pull them out one day? I wouln't rely on conduit as Hot insulation.
    It's really the other way around. You want to run everything in conduits but it's not sensible for UFH pipes because you care more that they are closely coupled to the slab in which they are embedded. (And also because they follow a very convoluted path so couldn't easily be pulled out)

    Depending on the hardness of the water you might want to change a DHW pipe before its structure degrades, and the structure will likely degrade within the lifetime of the building anyway. We've all seen surface mounted pipes in older buildings.

    Building regs and the associated compliance guide require hot water pipes to be insulated. PH also requires the cold pipe to be insulated, FWIW.
    •  
      CommentAuthorfostertom
    • CommentTimeApr 28th 2022
     
    All gd POVs - I feel clearer now.
  11.  
    So a 24mm conduit in the floor will suffice.

    Could you run 10mm to whb across a 2m distance t'd from a 15mm?
    • CommentAuthorrevor
    • CommentTimeApr 29th 2022
     
    The recommendation is that cold water should not be allowed to go more than 20 deg C it is a health issue more than anything else.
    • CommentAuthorborpin
    • CommentTimeApr 29th 2022
     
    Posted By: VictorianecoCould you run 10mm to whb across a 2m distance t'd from a 15mm?
    For a HB, 10mm will be more than enough. Also means it will run colder quicker.
  14.  
    The run length on the pipes in that picture is about 2 metres from the hot water tank and cold supply.

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