Radiator won't heat up

Discussion in 'Plumbers' Talk' started by Naeblis, Sep 1, 2018.

  1. Naeblis

    Naeblis New Member

    Hi, I'm new here and I'm looking for advice on one of my radiators, please.

    I understand the very basics of my heating system: I can repressurise my boiler, bleed my radiators and change my valves. I know that black sludge can cause cold spots, which can also be caused by trapped air. That's about the extent of my knowledge and ability at the moment.

    We had a new boiler and radiators with thermostatic valves fitted about a year and a half ago.

    A couple of days ago I noticed that my boiler pressure was low, so I sorted it out. I slightly overdid it (not by much, but the needle was right at the top of the green part of the dial and kept rising because I hadn't fully turned the water off), and needed to bleed the radiators to release a bit of the pressure. I got the other half to do it while I kept an eye on the dial, but only did the 3 downstairs radiators.

    Last night the heating came on but the bathroom radiator wouldn't heat up at all. It's the second to last one in the system and all the others were fine. The intake pipe was hot and the radiator is definitely turned on.

    Today I bled the upstairs radiators and as soon as I turned the key slightly discoloured water came out, but there was nothing at all from the bathroom one, not even the hiss. We had the same problem with this one before we had the new radiators fitted, but this is the first time it's happened since we replaced the system.

    If anyone has any advice I'd be very grateful. Thanks.
     
  2. terrymac

    terrymac Screwfix Select

    Close the thermostatic valves on all other rads , make sure bathroom rad valves are open and run c/heating. This should bring bathroom rad on. If it doesnt one or both of its valves are duff or pipework to it blocked.
     
    DIY womble likes this.
  3. Naeblis

    Naeblis New Member

    Thanks, I'll try it out.
     
  4. terrymac

    terrymac Screwfix Select

    Bathroom rad may collect air and need to be bled during the process.
     
  5. Heat

    Heat Screwfix Select

    It is much more likely to be the air screw hole is blocked with a very tiny bit of dirt.
    Very common fault.
    You just need to turn fully off BOTH valves on the radiator and remove bleed screw and poke a large needle in the air vent.
    Expect there to be a rush of air for a few seconds. Keep an old towel ready just in case.
    Screw the air screw back in and open valves to that rad and then bleed the air from it.
     
  6. Naeblis

    Naeblis New Member

    Terrymac's way worked first time. Thanks to you both for your advice.
     
    Heat likes this.
  7. rogerk101

    rogerk101 Screwfix Select

    It sounds like your system could do with a clean-out.
    You could do the job properly with an appropriate cleaning additive added to the system and then powerflush it after it has been running for a few days. Alternatively, you could install an inline magnetic filter, run it for a few days, and clean out the filter. Repeat the filter cleaning process every few days until there is almost no build-up and then do it once a year thereafter.
     
  8. Heat

    Heat Screwfix Select

    Yes, something very strange that a radiator won’t bleed any air on a pressurised (sealed) system.
    Every radiator should bleed no problem when you have 1 bar or more pressure. An open gravity fed system is a different story and can have air locks especially on badly done pipework.
     
  9. Naeblis

    Naeblis New Member

    Thanks. We had a powerflush done a couple of years ago, and the filth that came out was incredible. Unfortunately it wasn't enough to make the radiators work properly so we replaced the lot. The water that comes out now when they're bled looks clear until it pool in the jug, and then it's only very slightly discoloured. Would they still benefit from a clean out, do you think? I tried terrymac's advice, and as of last night the bathroom radiator seemed to be working fine.
     
  10. rogerk101

    rogerk101 Screwfix Select

    Have you got a filter installed?
    If so, what does it look like?
    If not, it'd be a good idea to put one in --- you'd be astounded at what it collects in the first year or two, even with a good inhibitor in the water.
    After a couple of years, it'll be almost clear and you can probably drop filter checking back down to only if you're doing work that requires pressure top-up.
     
  11. Heat

    Heat Screwfix Select

    Magnaclean 28mm XP is an excellent filter if you have 28mm pipes. Brilliant simple design.
    Filters are more important on open systems or those converted from open to sealed. In fact any system that has some old dirty pipes or rads.
    You need chemical to lift the dirt into suspension to allow it to flow to the filter.
    I was shocked to see what dirt was gathered from a few metre run of old pipework on a job I linked to
    On an all brand new sealed system, a filter isn’t really needed imo
     
  12. Naeblis

    Naeblis New Member

    I don't know if we have a filter fitted, but I'm going to look into it.

    Thank you all for your advice, you've been very helpful.
     
    Heat likes this.
  13. Dennisplamer

    Dennisplamer New Member

    If you have a radiator that's not heating is usually happen due to trapped air in it. You can get rid of this problem by opening & closing the valve on the water pipe above the boiler.
     

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