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Thread: Air bubbles in filter

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    Air bubbles in filter

    Hello again, thanks to you wonderful TFP folk the water chemistry problems I had have been resolved and all as stayed fine... but unfortunately a problem of a rather different nature has now developed. I've read all the threads I can find on air in filter problems but nothing on the crazy situation I seem to now have. This appears to be an air in the filter problem with a difference!

    I have one skimmer and shut off valve and duel sumps with a shut off valve prior to the pump inlet.

    Everything is working fine when the circulation is running, PSI is good and not even the slightest air bubble appearing in the pump basket or the large sight dome on top of the filter. (Triton 24 inch sand filter) This ONLY effects the filter... not the pump... absolutly no sign of an air bubble in the pump at any stage... whether on or off. Weirdly it can happen within a few minutes, sometimes 15 minutes... and sometimes even at least an hour and a half after filtration has stopped before the problem becomes noticable... and then it slowly begins!

    Just the faint sound and feel of water trickling through pipes and out the waste pipe to start with. A few minutes later the tricke sound turns into a very noticeable loud glugging sound and large air bubble appear rising up from the depths of the filter into the dome. It can rapidly increase and the water level in the filter disappears from sight within a minute or two like bath water going down the plug hole! I'm almost certain that the water stops level with the bottom of the waste pipe out of the multiport... the glugging noise stops and all is quiet. Still no sign of air or loss of water in the pump... even the following morning.

    On restarting on filtration the pump remains totally full, there is absolutly no drop off in the pump at any time but I'm looking at a filter dome full of air and water jets! I bleed the air off manually from the bleed valve on top of the sight dome and eventually the water rises and everything is going full blast again. If I don't bleed it off it can take ages for the bubbles to stop appearing out of the returns into the pool.

    After doing all the usual leak detection checks for a leak on the suction side of the pump including using leak detection spray on solvent joints, making sure everything is very tight... and looking for little spurts of water on switch off.... and finding nothing whatsoever wrong I decided to renew ALL seals and gaskets.

    I undid ALL pipe work that's not solvent welded, disconnected the pump and renewed the internal seals, including a new trap gasket! I completly removed the multi-port valve and removed the old spider gasket and cleaned out the channels and fitted a new spider gasket, perimeter top gasket, two handle spindle seals AND fitted a new handle depression spring. I took the dome off and renewed the perimeter gasket and air bleed valve seals. I aqualubed everything! All threaded joints connections were cleaned and refitted with new thread tape and tightened to within an inch of their lives!

    Nothing changed!

    In desperation I disconnected the heat sink pipe connections from the in/out header on the side of the Laars Lite2 boiler wondering if they could be letting in air causing some kind of back siphoning. The flange compression gaskets did look a bit hard and brittle so I replaced them. I also undid the metal to plastic heat sink connections at the bottom ends... they seemed fine so just and cleaned them up and lubed them and made sure they were tight.

    Everything now looks clean, tight and good.

    The problem still exists in the multiport valve 'closed' position but doesn't appear when set for 'circulation' but then of course the filter IS isolated... and I DO get a big air gulp and just a quick spurt of air bubbles out of the returns on 'circulation' mode start up. That's how I'm running at the moment. I turn the filtration off with the filter full and quickly turn the valve to 'circulation' and it just stands there overnight. In the mornings I let it start up on timer with a big gulp and then turn the valve to 'filtration' when I'm up and around.

    I've tried running with one each of the skimmer and drain valves in the closed position in turn... but no joy.

    Now I dunno what else to try... just wondering if one of those skimmer/drain shut off valves could have a faulty internal seal... (they are the full flow type) but there has been nothing visible from the outside, they both seem dry and the connections are very tight. I've tried everything I can think of... could it be a leaky valve that's not showing itself...

    I'm very puzzeled because of the incredibly long time it can sometimes take before it becomes apparent there is a problem... in conjunction with the fact that it CAN happen sometimes within a couple of minutes. Nothing seems to be consistent!

    Even if it is an underground leak why can it take so long sometimes for the air in the filter to become noticable? Also how can it get in with the skimmer/drain valves in the closed position?

    If anyone has any thoughts or ideas of what I should try next... I would be VERY grateful to hear of any suggestions or ideas anyone can come up with.
    8 yr old outside in ground vinyl liner rectangular 15' x 30' with 7' 'hopper shape sloping wall' deep end. (Think about 14,000 US galls but not sure!) Pentair Triton 24"sand filter (filled with recycled glass beads) Sta-Rite one-a-half HP single speed pump. Two pool returns. Gas boiler. Test kits = LaMotte DPD liquid regant ColorQ Pro7... supplemented with LaMotte FAS DPD for FC/TC when slamming. Live in southern UK

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    Richard320's Avatar
    Join Date
    Jan 2010
    San Dimas, CA (LA County)

    Re: Air bubbles in filter

    I had a similar problem for a few weeks that I determined came from the air bleed valve on top. Something went weird with the internal O-ring. I noticed sometimes I just couldn't get the thing to lock down easily. Not every time, either. It wouldn't leak with the filter on. I noticed the air in the returns and bled it out on startup, and when I checked it again two hours later, no air escaped. The next day, same thing, filter full of air and no water leaks.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: Air bubbles in filter

    Hi Richard and thanks for your comments. I took the pressure gauge/air bleed off and renewed the little 'o' seals just because I decided I just as well renew them as I was renewing all other the rings and gaskets I could think of! It was a good job done anyway so I don't view that as a wasted exercise and even though I haven't 'cured' anything... and hopefully I've stopped anything else deteriateing for a while!! I've not had any operational trouble with the bleed valve before or since but I'll have another look at it. Also if it did leak then with the filter dome full right the way up to it wouldn't the water level would just calmly get gradually lower? After having the pump running for a while I don't even get an air bubble in the peak of the filter dome it's 100% full of water and it can stay that way for up to a couple of hours!!

    Turn off the pump and it stays like that... peaceful as you could wish for.
    But anything up to a couple of hours later it's total mayhem at times. The first indication that something is starting to move is just the faintest trickling noise and I can just feel the water moving in the multiport inlet and the waste outlet pipes, that can go on for several minutes but weirdly with no drop in the water level at the top of the dome till a big air bubble rises up from the bottom of the filter, slowly followed by more, sometimes thats how it goes, slowly appearing large air bubbles just lazily drifting up from the depths till the water very slowly disappears calmly out the dome... other times it's very fast... after the faint trickling loads of air bubbles appear shooting up from the bottom of the filter, lots of glugging and gurgling and the water has gone within a few seconds, by quickly switching the multiport to 'circulation' whilst it's happening... I can stop it! I just don't understand how the filter can sit there quite happily for so long before it all happens or why it stops in 'circulation mode. But I don't THINK it just happes when set to filtration, it's just THAT setting makes it more noticable.
    I'm pretty sure air is present when set to 'circulation' because when I start the pump in that setting after everything being off for a while... I get an initial gulping/glugging noise at the return jets and a big whoosh of air bubbles into the pool. It only a momentarily event on the initial start of the pump... then it's fine... but it does seem to suggest proves air is getting in and is present somewhere. Goodness knows where cos I dont't!!
    It's the time it takes for the air to cause a problem, why it only shows after switch off, why the filter can stand there full of water overnight when set to filtration with no apparent air in the filte and howcome I don't see it in the pump that's got me puzzled. But whatever... air IS getting in and air can't get in by magic... logically air can only be sucked in when the pump is sucking. I initially thought that a big pocket of air was staying in the bottom of the filter until possibly some sort air equalisation between the point of entry of air and the waste exit from the multiport releases the trapped air and let's it rise to the top. But if THAT is the case... why, when I switch to circulation whilst the filter is still full up to brim with water.... doesn't any air bubble appear when I switch back over to filtration... which it does just as smooth as you like. Left switched off on filtration overnight the filter dome is still full of water the next morning. I start the pump manually so I'm there to see it and NO air appears when I swap back to filtration. I dunno, I'm grasping at straws and going round in circles just trying to imagine what's goin on! But hey... thanks for your comments!
    8 yr old outside in ground vinyl liner rectangular 15' x 30' with 7' 'hopper shape sloping wall' deep end. (Think about 14,000 US galls but not sure!) Pentair Triton 24"sand filter (filled with recycled glass beads) Sta-Rite one-a-half HP single speed pump. Two pool returns. Gas boiler. Test kits = LaMotte DPD liquid regant ColorQ Pro7... supplemented with LaMotte FAS DPD for FC/TC when slamming. Live in southern UK

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