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Not a gardening question, need help with a radiator


Our rads have started making a whooshing/hissing sound when turn up to number 4. I have been on You Tube and the only info I get is about bleeding. They do not need bleeding because they are hot at the top and cold at the bottom.

When we turn on the hot water tap, the noise stops for a while then comes back.

Any help or advice would be appreciated.


  • nutcutletnutcutlet Posts: 27,431

    Half full of sludge and need a flush through?

    In the sticks near Peterborough
  • PalustrisPalustris Posts: 4,304

    Try draining one from the bottom. You need to catch the 'liquid' which comes out as it is usually extremely filthy and will stain carpets (Found that out the hard way). Then bleed the system through.

    Also try bleeding the pump itself. there is usually a valve on it somewhere. Different places for different pumps so cannot help with location.

  • ClaringtonClarington Posts: 4,949

    Mark - they should be hot throughout, cold at the bottom means that you need to flush the system of the sludge that is stopping your radiators working effectively.

  • OK, thanks all. 'Sludge' seems the common word used here. The whole system is due for a service soon, I'll mentioned it to the chap when he comes.

  • Draining the system down and adding an inhibitor would seem the way to go.

  • Pete.8Pete.8 Posts: 11,319

    Do you know what sort of plumbing your central heating has?

    If you have a 1-pipe system (probably pre-1970's) then a pressure-flush will not help, due to the design of the system. Each rad needs to be removed and flushed.
    If you have a modern 2-pipe system, then a good flush may help.

    I'm not a plumber, but have been having similar problems. After having several heating 'experts' advise all sort of crazy things, at last I've found someone who knows what he's talking about.
    I've got a 2400mm x 700mm rad that's not getting hot at the bottom. This is due to my old 1-pipe system. After about 4 hours the whole rad is hot, it just takes time - even with a 42Kw boiler. 
    I have found that balancing the rads has helped a lot. My new plumber has also pointed out that thermostatic rad valves usually do not work with 1-pipe systems. I removed all my TRV's and the rads are MUCH hotter that they were on MAX with TRV's in place.

    Good luck & Happy New Year

    Billericay - Essex

    Knowledge is knowing that a tomato is a fruit.
    Wisdom is not putting it in a fruit salad.
  • Thanks Pete, the system is only two years old and still under warranty. As already mentioned we are having it serviced soon so I'll get the chap to have a look.

    Happy New Year to you tooimage

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