Going from 10mm back to 15mm

Discussion in 'Plumbers' Talk' started by jcswright, Aug 31, 2015.

  1. jcswright

    jcswright New Member

    Hi

    All the radiators in my flat have 15mm pipework, except for one in the downstairs hallway which is fed by 10mm. The 10mm comes from the end of the 15mm run of upstairs radiators, and passes down through the concrete slab on top of the garage, to the hallway radiator. The hallway radiator is the only one down there.

    I'm converting the garage, which is next to the hallway, and would like to effectively move the hallway radiator into the garage (remove the hallway radiator and put a new one in the garage from the same feed). I'll be insulating the garage well, so although the new radiator will be larger than the hallway radiator was, it shouldn't need to be huge. For various reasons, including the concrete slab over the garage, getting to the 15mm from the upstairs radiators would be a big upheaval. On the other hand, I can relatively easily get to the existing 10mm in the ceiling of the hallway.

    Would it be OK to convert the 10mm back to 15mm at that point, and continue as normal with 15mm pipe and fittings? The hallway radiator heats up nice and fast as it is, and the system isn't much loaded by the other 4 radiators (3 of which have TRVs).

    There would be about 3m of 10mm pipe before it's converted back to 15mm. I realise it's not ideal, but if it really makes no difference which I use then I might as well use pipe/fittings I've already got and just carry on as normal.

    Can anyone see any downside to this? There is no more potential for further expansion of the flat, so I'm not creating a bottleneck for future work - if this works OK then that's all it needs.

    Thank you!
     
  2. What size (output) rad are you proposing? There is obviously a limit to the size of rad that 10mm can support. Off the top of my head that's about 1.5kW but I'd have to work it out to be certain. (Cue heating engineers . . . ) So, if it's less than that then why change from 10mm? I've just done a house where all the ground floor drops were in plastic 10mm to a back box centrally behind the rad and then to 10mm/15mm push fit chrome elbows into the valves. Very tidy.
     
  3. jcswright

    jcswright New Member

    Hi, thank you for the reply.

    It'll be somewhere between 800-1000W - I haven't worked it out yet but I'm sure it'll be under 1.5kW. In truth my main reason for going back to 15mm is that I've got plenty of 15mm fittings/pipe (I'm DIY not trade so I might as well use what I've got) and the pipes will come straight out of the wall so there won't be much to see whether it's 10 or 15mm. I see what you mean about the 10mm though.

    Also, doing it this way means the lowest point of the whole system will be 15mm not 10mm. I've already taken the radiator off the wall, and what came out looked clean enough to drink - and it was the lowest radiator - so I'm not _too_ worried about sludge though...

    What's good is that nobody's come on here and said "you can't go from 15mm to 10mm and back to 15mm", so I might as well crack on!

    Thanks
     
  4. Crowsfoot

    Crowsfoot Screwfix Select

    A professional plumber would not do this because it would look a DIY job but as it is a DIY job anyway.....:)
     
  5. jcswright

    jcswright New Member

    Thanks Crowsfoot - would you take up the floor upstairs and replace all the 10mm, or stick with 10mm all the way instead of going back to 15mm as I was planning to?
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice