Posting a message to the forum will remove the above advertisement
  1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.
  2. Checkout our Plumbers Insurance area - heavily discounted Public Liability Insurance and Van Insurance specifically designed for plumbers.

Discuss Max Size of Radiator with 10mm Pipes? in the Central Heating Forum area at

  1. LesArcs

    LesArcs New Member

    Hi. I was hoping to change a radiator in my sitting room for a significantly larger one, but having read a few bits and pieces on the web, I'm not sure whether it is feasible. The existing radiator is a double panel, double fin radiator measuring about 1200 long by about 700 high and is fed by 10mm diameter pipes. I think the output of the existing rad is about 8200BTu / 2400W. I was hoping to replace this with something larger but am now not so sure, due to the diameter of the pipework. Is there a rule of thumb for the maximum size of radiator that can be used in conjunction with 10mm pipes? Would appreciate any advice.
  2. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Depends on a lot

    Copper plastic

    Any fittings etc

    Length of run

    TBH if the existing one works I wouldn’t increase the rad by much
    • Agree Agree x 2
  3. chris watkins

    chris watkins Plumber

    as above
    but to give you a guide - based on 10mm copper around 2400Watts if you are running it with boiler on max i.e. 11degC between the F&R or 4300Watts if it is 20degC.
  4. Rob Foster

    Rob Foster Top Contributor!!

    my experience is practical ..I tried 3.2 kw on a 15 mm supply
    on two rads only one at a time really did well ...1o mm will be worse ..Rob Foster aka centralheatking
  5. Best

    Best Trusted Plumber Top Contributor!!

    Rob, 15mm should do about 6 kw no problem if system is balanced.
    I would think of it as having a limit of 2 very big radiators, or 4 or 5 smallish radiators.
    I was always told rough guide was 15mm for 20,000 btus (6kw) max
    and 22mm for 60,000 btus (18kw) max for open vented heating systems.
    Sealed system would be more capable.
  6. Rob Foster

    Rob Foster Top Contributor!!

    yes ur right I meant 2x 3kw big double rads ...on a 15mm ...I was not clear enough
Similar Threads - Size Radiator 10mm Forum Date
Radiator blanking plug size Central Heating Forum Jan 27, 2019
Potterton statesman 45/50 nozzel size? Oil and Solid Fuel Forum Feb 8, 2019