1. Visiting from the US? Why not try DIYnot.US instead? Click here to continue to DIYnot.US.
    Dismiss Notice

adding bigger pipes to 8mm system

Discussion in 'Plumbing and Central Heating' started by jl81, 10 Nov 2019.

  1. jl81

    jl81

    Joined:
    10 Nov 2019
    Messages:
    6
    Thanks Received:
    0
    Country:
    United Kingdom
    hey,
    we have a pressurised microbore 8mm system and combi boiler - for 90% of the house - perfect all piping hot.

    1 radiator (1.4mx50cm double) gets warm-ish and stone cold at bottom. there dosent seem to be any restriction to flow with the radiator off and the system has been cleaned. Thinking we need to seal off the possibly kinked/too small pipes (yay sealed in plaster). and upgrade to 10 or 15mm pipework for this one radiator.

    2 questions
    1 - is the radiator too big for the pipework

    2 - had a couple of guys look at the job all bar one said doable - but pipe should be fine (want to 'clean' first - which we have tried) one stated that pipe is too small but adding larger pipes to 1 or 2 radiators could screw the rest of the system up and stop it working. Is he right?

    just wish there was a general consensus on the issue/solution
     
  2. Sponsored Links
  3. muggles

    muggles

    Joined:
    28 Oct 2005
    Messages:
    13,239
    Thanks Received:
    3,036
    Location:
    Daventry
    Country:
    United Kingdom
    Does that radiator work if you turn all the others off?
     
  4. Iamchamps

    Iamchamps

    Joined:
    24 Sep 2016
    Messages:
    1,037
    Thanks Received:
    162
    Country:
    United Kingdom
    Could just be a balancing issue.
     
  5. jl81

    jl81

    Joined:
    10 Nov 2019
    Messages:
    6
    Thanks Received:
    0
    Country:
    United Kingdom
    a hair better if anything.
    rad is 2.4kw btw.

    & tried balancing also nope. all are dialled down, this is wide open with hot inlet stone cold return, - and no obvious restricted flow on either.
     
  6. muggles

    muggles

    Joined:
    28 Oct 2005
    Messages:
    13,239
    Thanks Received:
    3,036
    Location:
    Daventry
    Country:
    United Kingdom
    Sounds like a blockage to me. Turn off the radiator valves and remove the radiator from the wall. Adapt a hosepipe so that it will fit onto a valve, run it outside then turn the valve on, see whether water flows freely. Repeat with the second valve
     
  7. jl81

    jl81

    Joined:
    10 Nov 2019
    Messages:
    6
    Thanks Received:
    0
    Country:
    United Kingdom

    Tried and it flows fine & crystal clear.
     
  8. alan999

    alan999

    Joined:
    15 Mar 2010
    Messages:
    139
    Thanks Received:
    6
    Location:
    Staffordshire
    Country:
    United Kingdom
    Has the radiator ever been really hot
     
  9. Killalot

    Killalot

    Joined:
    10 Nov 2019
    Messages:
    8
    Thanks Received:
    0
    Country:
    United Kingdom
    I had the same problem with both radiators in the conservatory I changed the pipe to 15mm had to leave about 1m off 8mm pipe because it was in the wall. Works fine now.
     
    • Like Like x 1
  10. Sponsored Links
  11. jl81

    jl81

    Joined:
    10 Nov 2019
    Messages:
    6
    Thanks Received:
    0
    Country:
    United Kingdom
    No.
    No matter what we did. It’s 2.4kw. Which is why I’m wondering if it’s too big for 8mm.
     
  12. alan999

    alan999

    Joined:
    15 Mar 2010
    Messages:
    139
    Thanks Received:
    6
    Location:
    Staffordshire
    Country:
    United Kingdom
    Possibly. If the radiator is already off and you are confident enough you could try fitting a length of pipe across the 2 valves. See if that heats up or not.
     
  13. Terrywookfit

    Terrywookfit

    Joined:
    19 Jul 2007
    Messages:
    5,740
    Thanks Received:
    1,086
    Country:
    United Kingdom
    Is this copper pipe how long is the run of 8mm + any elbows ??
     
  14. John D v2.0

    John D v2.0

    Joined:
    26 Aug 2016
    Messages:
    6,341
    Thanks Received:
    878
    Country:
    United Kingdom
    You can get a lot of heat through 8mm especially if the temperature drop is designed to be 20c or more but if the pump doesn't have enough oomph for the length it might not flow well
     
    Last edited: 11 Nov 2019
  15. jl81

    jl81

    Joined:
    10 Nov 2019
    Messages:
    6
    Thanks Received:
    0
    Country:
    United Kingdom
    Sorry it gets warm. We know heat is getting there and with the radiator off there isn’t any restricted flow from either pipe that we can see.
    Starting to wonder if giving a chemical clean might be an idea.
     
  16. jl81

    jl81

    Joined:
    10 Nov 2019
    Messages:
    6
    Thanks Received:
    0
    Country:
    United Kingdom
    Not 100% sure. Hunks are encased in plaster
    Think maybe 8-10m from manifold.


    Wouldn’t that flag on other radiators as well though? It’s just this one that’s a pain.
     
  17. John D v2.0

    John D v2.0

    Joined:
    26 Aug 2016
    Messages:
    6,341
    Thanks Received:
    878
    Country:
    United Kingdom
    8 to 10msa lot, as that's at least double that for flow and return.
    I did the calculations for a new cavity wall bedroom and decided it was ok on a basic 3m head pump with 5m each way, that was similar pipe, 10mm speedfit with no joints. So having double that, assuming it's all 8mm copper would be a challenge.
    Are the other rads similar distances on 8mm too and similar sized?
     
Loading...

Share This Page