continuously getting air in system

Discussion in 'Plumbing and Central Heating' started by zooankski, 12 Jul 2009.

  1. zooankski

    zooankski

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    Hi all

    I am having problems with air getting in to my open vent system. I have removed all the lagging from the pipes in the loft as i thought air might be getting in there and would appreciate an opinion on the layout as it does not look quite right to me.
    It appears to be a combined feed and vent all in 22mm but i think the feed should be lower down the pipe???
    Failing that can anyone sugest any tests i could carry out to try and isolate where air is being drawn in? I have turned the pump down to it's lowest setting but no joy there.
    I have noticed that air gets in irrespective of if the hot water only or heating is on so does that provide any clues?

     
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  3. DP

    DP

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    Fill the tumbler (sitting right of the expansion tank) with water and offer the glass to the vent. Now get someone to switch the heating on. See if the vent drinks the water. When system idle, water lever in the vent and expansion tank will be the same. For air to enter the system, water level in the vent has to drop past the tee that pump is fitted to. Cannot see that happening on a combined feed and vent pipes.

    Only thing I see wrong is existance of gate valve on the feed pipe- it should be removed.

    Air in the system could be a rad valve, loose fitting, loose rad plug or vent or even corrosion related.
     
  4. bengasman

    bengasman

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    How long have you had this problem?
    What has changes since it was installed?
     
  5. wilhelm

    wilhelm

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    when you say probs with air getting into system, I presume you are bleeding the rads, and air is coming out? are you sure air is coming out....cos air going in, makes the same sound.

    have you got any pipework going into concrete?
     
  6. Looking at the picture on the right it's set up for a combined feed & vent, however the pipework to the F&E tank has a vent pipe over the top of the tank, do away with this pipe, cut out the tee & replace it with an elbow.
     
  7. bengasman

    bengasman

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    Not a good idea.
     

  8. or cut it and stick a check valve and aav on the o/v so it can expel air but not suck air in.

    if the boiler is suitable conversion to sealed system would be another option.
     
  9. picasso

    picasso

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    have you just fitted a new pump?
     
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  11. DP

    DP

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    And I thought no valves of any kind could be fitted on vent or feed pipes (including things lings like pumps). Please correct me if I am wrong
     
  12. zooankski

    zooankski

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    BG fitted a new pump about 4 months ago. thinking about it, the problem has been worse since then so perhaps a pump problem?
     
  13. zooankski

    zooankski

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    the down stairs rads have pipework below the screed. I did think about a possible leak so turned the header fill off for a week and there was no loss. Not sure how else i could see if it was leaking?
    Is there a means of pressurising the system to check for leaks? ie block the feed and vent and put a bar or so of pressure in the system to see if it drops? (system turned off obviously!)
     
  14. Nige F

    Nige F

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    Perhaps a BG problem :idea: If you are paying them good money ...maybe even for a yearly service/repair contract :?:
     
  15. zooankski

    zooankski

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    Quick update, i borrowed a friends hydraulic pressure tester and sytem holds 3.5 bar no problem so i can rule out a leak i guess. I cannot see any signs of pumping over so am now scratching my head. Perhaps i will just opt for a sealed system and be done with it. :confused:
     
  16. bengasman

    bengasman

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    Penny just dropped. No leaks and problems started after new pump. Pump could be upside down.
     
  17. basically with the the position of the cold feed and vent with the new pump would cause air ingress,due to pulling the level of water under the feed level. older pumps werent as effective as they are now.personally i think the cold feed is to near the water level.ps the gate valve aint gonna help and is a no no.have you tried to see if its fully open.
     
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