Do you ever bleed rads with heating on?

Discussion in 'Plumbers' Talk' started by Martin.Stone, Sep 26, 2021.

  1. Martin.Stone

    Martin.Stone Member

    I have air in my system when water is heating and I’m told to turn heat and water on to push the air to the rads, the plumber said it’s a myth that you have to turn heating off to bleed BUT it’s a safety thing. Do you ever bleed with heat on?
     
  2. pppmacca43

    pppmacca43 Super Member

  3. Martin.Stone

    Martin.Stone Member

    I have no way to pressurise the boiler it’s old and has no gauges or knobs on it
     
    Last edited: Sep 26, 2021
  4. pppmacca43

    pppmacca43 Super Member

    Ok so probably tank fed so should top itself up if so
     
    Martin.Stone likes this.
  5. exbg

    exbg Active Member

    Considering that Veissman is a heating manufacturer, I am surprised that they would publish a pageful of garbage.

    The reason that one turns the heating off, is to stop the pump. This allows the water to find its own level. Also, on some older systems, some of the rads can be under negative pressure with pump on - you can suck air IN to the rads with the pump on.

    OP: Exactly what is the problem? Is there a an actual malfunction, or just noisy?
     
    BillyBobToo and pppmacca43 like this.
  6. Martin.Stone

    Martin.Stone Member

    When the water is heating there is loads of air (gurgling)
    I haven’t had the heating on for months obviously and the plumber who replaced all my TRVs a month ago said try running water and heating together for an hour to push air up to rads.
     
  7. pppmacca43

    pppmacca43 Super Member

    Agree and definitely can suck in air on some systems, we have one at work that does so if we don’t turn the pumps off, but viessman do tell you to turn the heating off when u bleed it, although they say it’s so u don’t burn yourself lol, when I would say it’s cos it can suck air in and actually with the pumps on the air won’t be settled it will be being moved about.
     
    exbg likes this.
  8. pppmacca43

    pppmacca43 Super Member

    Have you tried venting radiators yet, just do it when the systems cold and everything is off. Start on the ground floor and work your way up. If your system is fed by a tank in the loft it should top itself up.
    Also if you have a immersion type cylinder in the cupboard there may be some air vents in there too that could be automatic but also may need manually venting.
     
  9. Severntrent

    Severntrent Screwfix Select

    If you have a " normal" system with the pump sucking the flow out of the boiler and then pumping it around your distribution system you won't be sucking any air in so bleed with heating on or off it won't make any difference. Possibly with heating on any air bubbles in the distribution pipework should be pushed forward and trapped in the radiators but if this should have already occurred if you have been running your heating previously.
     
  10. exbg

    exbg Active Member

    The problem is that the definition of "normal" probably changes with the age of the beholder ;)
     
    pppmacca43 likes this.
  11. exbg

    exbg Active Member

    Good point about the auto air vents. They are generally poor, and subject to leaks, which sometimes present themselves as crud on the valve. This then prevents normal operation. Also, many are found with the caps screwed right down, rendering them non auto.

    While on the subject, AAV's in lofts often allow air IN. If you hear one hissing, remove the cap totally and use a bit of leak detector solution, soapy water or spit to determine whether the valve is sucking or blowing.

    OP: We assume that the air/noise has started since the work was completed?
     
    pppmacca43 likes this.
  12. pppmacca43

    pppmacca43 Super Member

    Yeah some of the AAVs are awful, plumb centres own brand ones for example. Normally will fit flamco ones but they even fail now and again.
     
  13. Wayners

    Wayners Screwfix Select

    No. I don't
     
    pppmacca43 likes this.
  14. Martin.Stone

    Martin.Stone Member

    So I sat sweating for an hour with the heating on, bled the rads, tried again, bled the rads, tried again… all was quite quiet, this evening the water came on to heat and after having a bath the noise is back, gurgling in the pipes
     
  15. pppmacca43

    pppmacca43 Super Member

    Did you look in the cylinder cupboard to see if there were any air vents in there. If you aren’t sure take a photo of it and the pipework and post.
     
  16. Martin.Stone

    Martin.Stone Member

    There is a bleed valve on a pipe that sticks up and I did that one too
     
  17. exbg

    exbg Active Member

    Is yours a combi or an open system. The latter has a small header tank in the loft. If it does have a HT, observe the vent pipe above the HT while a second person turns on the heating. Does water discharge from that pipe? Is the HT warm (check now , there may still be warmth from earlier)
     
  18. dcox

    dcox Screwfix Select

    Do you have a magnetic filter fitted? Those trap air and need to be vented out.
     
  19. Martin.Stone

    Martin.Stone Member

    Nope
    , no magnetic filter, not even sure what that is lol
     
  20. dcox

    dcox Screwfix Select

    Looks like this and would probably be above or below your boiler.

    75384141-0963-4DAE-9E8D-EC047D51C3A0.jpeg
     

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