air lock in CH system..

Discussion in 'Plumbers' Talk' started by aak, Jan 5, 2019.

  1. aak

    aak Member

    dear all, quick update - after contacting a plumber and waiting for a response, I thought I'd make some more checks:

    checked all the connections in the connection box with a voltmeter, and it seemed that everything was being triggered and live when it ought to be.

    the pump needed bleeding again, and twice I had to encourage the impellor to start rotating with a little screwdriver nudge when there was air in it. not sure whether this means its on its way out, or whether thats normal when theres an air pocket in the system?

    after the suggestion of looking into automatic air release valves, I ended up taking apart the two that are in that first picture, which was easy to do by rotating the body to seal them off first. One was leaking quite a lot of water, but I had noticed that both were releasing a bit of air. both had fine, silty gunge in them, but seemed in good knick, and were very easy clean and put back together.

    the result is that everything seems to be running perfectly! no worrying kettling, no scary bangs, the pump seems to be running fine, teh valves seem to be operating when called, and the heating comes on when expected now. will keep watching to see whether this is just a temporary reprieve, but thanks very, very much to everyone who took the time to reply. @Allsorts 's post in particular I found most useful!

    so that results in the following queries:

    1) can a leaking AAV cause air to be drawn into the system? I'm wondering if the flow of water creates negative pressure that then draws air into the system (kind of indicated in the schematic below) - since cleaning the AAV's seems to have resolved the air lock issue.

    2) if there is an air pocket, is it possible for the pump to become seized?

    thanks again all! Air_valve_(model_and_workings).PNG
  2. Allsorts

    Allsorts Well-Known Member

    Nice diagram :)

    1) Yes, on a 'vented' system air can be drawn in wherever there's an opening or obvious 'leak', potentially even being drawn down the vent pipe itself, but for this to occur there would have to be a fault in the system or it having been very badly designed (eg header tank located barely above topmost radiator). On an otherwise well-functionng system, I understand the most common cause of this is a partial blockage in a pipe, I'm guessing located somewhere 'behind' the pump (ie on the sucky side) and before the vent pipe. This would cause a drop in pressure in that section of pipe, potentially causing it to draw in air from wherever it can - vent pipe, auto air vents etc.

    Hard to know whether you just happened to have a slow build-up of air that wasn't being vented off as it should, or whether you have bigger issues!

    2) If a pump isn't lubricated with water, the bearings can wear out pretty quickly, I understand. This added friction might well be enough for it to not kick-in when power is applied - which is what you seem to have experienced. If it's running ok now, then you may have got away with it...
    aak likes this.
  3. Allsorts

    Allsorts Well-Known Member

    I see you've also considered fitting a mag filter? Cool - if you do have a partial blockage, it would make huge sense to do this - along with a dose of cleaner.

    You have a 28mm return pipe? I think you'd be NUTS to not fit a good sized Magna filter with 28mm connections. I can tell you from experience that Magnacleans do not catch everything that goes through them, so the bigger the one you fit the more effective it will be (after suffering a blocked P2P exchanger for the second time, I removed my Mag Pro - which was collecting a steady amount of sludge) and temporarily plumbed in a Magnacleanse (the professional double-barrelled jobbie) and this immediately caught a healthy extra pile of junk.

    Do yersel a favour - fit a 28mm one, and fit it on the last section of the boiler return. The most it'l need is a couple of elbows, and compression ones will do.
    aak likes this.
  4. aak

    aak Member

    thanks much for that. it all seems to be working fine now, but I take the point that there may be an issue being masked. the header tank is a good 5 or 6 feet above the radiators, and probably 3 feet above the highest point of the boiler, so I dont think thats the issue.

    I have a magnaclean coming and someone to fit it in a week or two, so ill get a sanity check then from someone who isnt an amateur like me! unfortunately I read your message a little late and already ordered a 22mm filter - there's only four radiators being used on the system since its a flat, although there are another four that have been switched off which might be a problem if theres lots of debris.

    fingers crossed..
    Allsorts likes this.
  5. Allsorts

    Allsorts Well-Known Member

    4 rads ain't a lot :)

    You might consider - perhaps when summer comes - removing the unused ones one at a time (no need to fully drain down) and take them outside for a hose-through.
    aak likes this.
  6. aak

    aak Member

    Any ideas on how much it should cost to have a MagnaClean professionally installed chaps?
  7. Allsorts

    Allsorts Well-Known Member

    No idea. But if there is easy access to the pipe concerned and enough space around it, and - more importantly - if your system is easy to drain down and refill, then it should be very straight-forward.

    I'd imagine an hour's work would cover most eventualities, even slight complications?
  8. aak

    aak Member

    Yes I would have agreed - ok thanks. Looks like I’m getting 2 hours for my usual guy. Will look around, thank you.
  9. Allsorts

    Allsorts Well-Known Member

    Hang on a bit... Don't bleedin' listen to me - I ain't a plumber :oops:
  10. Allsorts

    Allsorts Well-Known Member

    Hang on a bit more...

    YOU drained your system, removed these air vents, cleaned them out, refitted them and refilled your system successfully? So what the hell are you doing paying someone else to fit a Magna for? :)
  11. aak

    aak Member

    ha! nearly right. I dint have to drain down to fix the AAVs - they twist lock at the base to seal off and access the guts!

    I have fitted a magnaclean before in a charity project because the boiler was in a shed and so if I screwed up I wouldn't cause too much trouble. but here its a block of flats so im a bit wary of a problem causing damage to neighbours!

    for 200 quid though im considering it though...
  12. dcox

    dcox Active Member

    I'd allow a couple of hours, so my bill would be around £170 to supply and fit a magnaclean pro if the pipework was straightforward.
    Allsorts likes this.
  13. aak

    aak Member

    Ok glad to get a sense of what it should be, very useful, thanks.
  14. Just a part timer

    Just a part timer New Member

    Hi guys dont mean to sound like an idiot but i believe i have an airlock in my bath hot tap which is located upstairs. I had a new bsthroom installed recently and my hot water has stoppef working in the bath. I have a mixer tap in kitchen and bathroom sink but two taps for the bath. The hot water is working in kitchen and bathroom sinks so i believe an airlock? I have done what ppl said and tried to connect kitchen mixer tap to a hose and kinked it then turned warm on firstt then cold. At this point when bathroom warm tap on air does splutter out with water but does stop when i do in the kitchen. Is this just a pain of sn airlock to get out? Should i keep trying? One main probkem is my mixer tap has a very short and awkward spout which i cannot get a conection to fit so i am literally holding a rubber tap and hose connector to the spout. Any help or advice appreciated guys. Thanks and sorry for posting here fisrt timer lol
  15. Allsorts

    Allsorts Well-Known Member

    I do agree with dcox - my 1 hour estimate would really involve everything being as completely simple as possible; easy access to the shut-off 'cock, easy access to the drain cock, easy access to the pipework in question, easy draining with no issues, and an easy refill with no air locks whatsoever. And then a test of the system.

    Ie - really pushing it.

    A 2 hour slot is far more realistic and gives elbow room.

    Aak - you've already fitted one?! Jeepers, man.

    Ooookkkaaaayyyy - you have a choice; go ahead as is, or DIY and fit a better one.

    See your boiler? That has a 28mm return pipe begging to be cut. The Magna Pro 2XP is designed for larger systems, but will do a better job of smaller ones like yours, and has 28mm fittings. A 188mm section of pipe is removed and - cut in two - this will allow you to fit the filter cranked out from these pipes for good access - ie you don't need to buy any extra pipe.

    Two 28mm brass comp elbows, a wee pot of Fernox Hawk, and small rotary cutter and a wrench or two.

    Jobbie jobbed.

    You can do this, and you can fit a better, larger filter, and you can monitor it afterwards and it won't cause any problems.

    But you'd have to sell off the one you've already bought.

    Or else get a plumber in.
    aak likes this.
  16. Allsorts

    Allsorts Well-Known Member

    Hi JaPT.

    Really should post on a new thread. You will get helpful replies. :)

    (PS - and answer on the new thread - is your bath cold tap from a tank or mains-driven?)
  17. Just a part timer

    Just a part timer New Member

    I will try lol
  18. aak

    aak Member

    Only just saw this reply - thanks very much for that. I haven’t drained down this system before but this may well be the route to take for me. Thanks again for the detailed post.

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