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Thread: air in return lines

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    air in return lines

    I recently replaced my filter and pump and have noticed air bubbles (particularly at pump start up) in my return lines into the pool. This obviously implies a suction side leak which I have had before and was previously able to locate and seal a connection. This time, the strange thing is that I am not seeing any air bubbles in the pump basket. Just air bubbles in the pool from the return lines. I have turned the main drain off and still have the air in the returns. I have turned the skimmers off and the main drain back on and still have the bubbles in the return. In each instance I am not observing any air bubbles in the pump basket.

    Any ideas? Is is possible to be sucking air into the pump without being able to observe bubbles in the pump basket?
    Mike
    20,000 gallon in-ground gunite with attached spa
    Pentair Cartridge Filter
    3/4 hp Sta-Rite Pump
    2 hp Whisperflo Spa Pump
    Ray-Vac cleaner

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    JasonLion's Avatar
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    Did you manually bleed the air out of the filter? Some of the systems that automatically bleed air out of the filter can take quite a while to get all the air out and there will be bubbles till then.

    Another possibility is if you have a SWG. A SWG will put small bubbles into the returns when it is running.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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  3. Back To Top    #3
    Quote Originally Posted by JasonLion
    Did you manually bleed the air out of the filter? Some of the systems that automatically bleed air out of the filter can take quite a while to get all the air out and there will be bubbles till then.

    Another possibility is if you have a SWG. A SWG will put small bubbles into the returns when it is running.
    I did manually bleed the air and am still getting air back through the returns. I do not have a SWG. I am baffled as it would stand to reason that I would see the air in the pump basket if it was being sucked in from the suction side. There is a lot of air coming through the returns at start-up that slowly dwindles but there remain "spurts" of air on a continuing basis.
    Mike
    20,000 gallon in-ground gunite with attached spa
    Pentair Cartridge Filter
    3/4 hp Sta-Rite Pump
    2 hp Whisperflo Spa Pump
    Ray-Vac cleaner

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    Quote Originally Posted by Pool in Carolina Blue
    Quote Originally Posted by JasonLion
    Did you manually bleed the air out of the filter? Some of the systems that automatically bleed air out of the filter can take quite a while to get all the air out and there will be bubbles till then.

    Another possibility is if you have a SWG. A SWG will put small bubbles into the returns when it is running.
    I did manually bleed the air and am still getting air back through the returns. I do not have a SWG. I am baffled as it would stand to reason that I would see the air in the pump basket if it was being sucked in from the suction side. There is a lot of air coming through the returns at start-up that slowly dwindles but there remain "spurts" of air on a continuing basis.
    Carolina,

    You obviously understand the system so your post is easy to follow. I'm gonna' guess (not good) at some possibilities:

    1. air could be entering around pump basket lid and pulled into pump befrore you see it.....not likely because you said it diminishes after startup

    2. So given the fact that it diminishes, it (the air) must be accumulating in a resevoir while the pump is off.....making me think this: I would suspect the tiniest of suction side leaks that is virtually undetectable with the pump running. Then, when the pump is off, that leak allows air into the system which, sooner or later, works it's way to the top of the filter....hence, the large volume of air when you start up but then diminishing as the air gets pushed out of the filter.

    That's a puzzling problem but air in the system can just about only come from a suction side leak.
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  5. Back To Top    #5
    Quote Originally Posted by duraleigh
    Quote Originally Posted by Pool in Carolina Blue
    Quote Originally Posted by JasonLion
    Did you manually bleed the air out of the filter? Some of the systems that automatically bleed air out of the filter can take quite a while to get all the air out and there will be bubbles till then.

    Another possibility is if you have a SWG. A SWG will put small bubbles into the returns when it is running.
    I did manually bleed the air and am still getting air back through the returns. I do not have a SWG. I am baffled as it would stand to reason that I would see the air in the pump basket if it was being sucked in from the suction side. There is a lot of air coming through the returns at start-up that slowly dwindles but there remain "spurts" of air on a continuing basis.
    Carolina,

    You obviously understand the system so your post is easy to follow. I'm gonna' guess (not good) at some possibilities:

    1. air could be entering around pump basket lid and pulled into pump befrore you see it.....not likely because you said it diminishes after startup

    2. So given the fact that it diminishes, it (the air) must be accumulating in a resevoir while the pump is off.....making me think this: I would suspect the tiniest of suction side leaks that is virtually undetectable with the pump running. Then, when the pump is off, that leak allows air into the system which, sooner or later, works it's way to the top of the filter....hence, the large volume of air when you start up but then diminishing as the air gets pushed out of the filter.

    That's a puzzling problem but air in the system can just about only come from a suction side leak.
    DU,

    Tis a head scratcher. Your guess makes sense. One thing I have not checked are the gaskets in the jandy valves that control the skimmers, main drain, and spa drain. I read earlier today that they could be a source of air if the gaskets have gone bad. Still doesn't explain the lack of bubbles in the pump basket. On another note, my old 60 sf de filter used to run at about 18 psi with a full rated 2 hp whisperflo that it was paired with. My new set-up is a 3/4 hp full rated sta-rite max-e-pro with a 48 sf cartridge style de filter. The normal operating pressure now is only 5 psi. The flow in the returns is good so I think everything is operating fine but I wonder if this suction leak could be a reason that my operating pressure dropped so significantly?
    Mike
    20,000 gallon in-ground gunite with attached spa
    Pentair Cartridge Filter
    3/4 hp Sta-Rite Pump
    2 hp Whisperflo Spa Pump
    Ray-Vac cleaner

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    No, I doubt a leak apparently that small would have any effect on you system psi.

    That's a very low psi, however.....not very normal at all. It does sound to me like there is an issue there. It might be a partial blockage on the suction side or something about your pump not performing at max.

    Do you have faith in your pressure guage? That's a common problem.
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Quote Originally Posted by duraleigh
    No, I doubt a leak apparently that small would have any effect on you system psi.

    That's a very low psi, however.....not very normal at all. It does sound to me like there is an issue there. It might be a partial blockage on the suction side or something about your pump not performing at max.

    Do you have faith in your pressure guage? That's a common problem.
    I have tested two and the pressure reading is exactly the same for each. I too am worried about the pump; I do not use my Jandy Ray Vac (pressure cleaner that does not require a booster) but I wanted to test the pressure on it so I pulled it out of the pool shed and hooked it up to the dedicated cleaner return line (with all of the flow from the pump directed to it) and checked the pressure on it. It immediately ran at 35 psi so it would seem that the pump is working fine. Having said that, I never directed all of the flow from the old 2 hp whisperflo to the cleaner line so maybe 35 psi isn't great pressure by comparison.

    I called Pentair previously and they indicated that 5-6 psi is low but not out of the realm of possibility given my pump/filter sizing. How do you test for a blockage?
    Mike
    20,000 gallon in-ground gunite with attached spa
    Pentair Cartridge Filter
    3/4 hp Sta-Rite Pump
    2 hp Whisperflo Spa Pump
    Ray-Vac cleaner

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    CB,

    Mas985 will probably see this....he may have some ideas for your low system psi.

    Just a note....35psi is an absolute blockage and, generally speaking, about all any constant speed pool pump is capable of producing. In other words, with a wide open suction side and a completely blocked pressure side (close the valves), 35 psi is about all you'll get.

    Back to the first issue.....try turning off the pump for 5-10 minutes and see how much air goes to the returns. Then, shut the pump off for several hours and, if the air is much greater than before, sorta' confirms that air is accumulating in the top of the filter.

    Is it a Cart or DE filter? I wonder if the inside design of the filter is such that an o-ring could be installed in such a way that it closes when pressure is applied to it (pump on) but then it allows air to leak back when the pump is turned off.....I just don't know enough about carts or DE's.
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Quote Originally Posted by duraleigh
    CB,

    Mas985 will probably see this....he may have some ideas for your low system psi.

    Just a note....35psi is an absolute blockage and, generally speaking, about all any constant speed pool pump is capable of producing. In other words, with a wide open suction side and a completely blocked pressure side (close the valves), 35 psi is about all you'll get.

    Back to the first issue.....try turning off the pump for 5-10 minutes and see how much air goes to the returns. Then, shut the pump off for several hours and, if the air is much greater than before, sorta' confirms that air is accumulating in the top of the filter.

    Is it a Cart or DE filter? I wonder if the inside design of the filter is such that an o-ring could be installed in such a way that it closes when pressure is applied to it (pump on) but then it allows air to leak back when the pump is turned off.....I just don't know enough about carts or DE's.
    Dave, are you saying I have a blockage? I think you are right in that air is for sure accumulating in the top of the filter. It is a cartridge style filter.
    Mike
    20,000 gallon in-ground gunite with attached spa
    Pentair Cartridge Filter
    3/4 hp Sta-Rite Pump
    2 hp Whisperflo Spa Pump
    Ray-Vac cleaner

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    Dave, are you saying I have a blockage?
    No, not at all.

    I was commenting on the pressure reading you got when you hooked up the Ray Vac. That indicated virtually no flow on the pressure side of the pump because pool pumps are incapable of producing much more than that. I would take from that test that your pump IS producing the energy you would expect.
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Quote Originally Posted by duraleigh
    Dave, are you saying I have a blockage?
    No, not at all.

    I was commenting on the pressure reading you got when you hooked up the Ray Vac. That indicated virtually no flow on the pressure side of the pump because pool pumps are incapable of producing much more than that. I would take from that test that your pump IS producing the energy you would expect.
    Thanks for the insight. The terminology was a little over my head. I am very appreciate of the time you have spent helping me with this issue.
    Mike
    20,000 gallon in-ground gunite with attached spa
    Pentair Cartridge Filter
    3/4 hp Sta-Rite Pump
    2 hp Whisperflo Spa Pump
    Ray-Vac cleaner

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    Possibly???

    Most everyone here is a better source than me, but I thought I would share my experience in case it helps.

    The "air always comes from the suction side" has always puzzled me.

    I have a known leak in my heater (I'll fix it after my Daughters pool party this weekend). I believe that would not be the suction side. Yet every time the system is turned off, this leak "becomes" the suction side. I can hear it sucking as it is in a fitting right by the shutoff switch. It fills the heater, and filter with air, even the pump basket ends up empty by the time I turn it back on. Then when fired back up I have Air in the lines.

    So maybe you also have a Leak in the parts of the system you haven't checked yet, and it only "becomes" the suction side after it is turned off for a while.
    15x32 Lazy L Inground / Concrete - 25,000 US Gal 1979 build
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    MJ,

    Your case sounds similar to the situation I attempted to describe wherein his filter didn't leak until the pump was turned off.

    If your heater doesn't leak water with the pump on, that's pretty unusual...but not impossible.

    By far, most leaks on the pressure side of the pump will show themselves by leaking water with the pump on. That they draw in air with the pump off is certainly true but that's typically not how you discover them.
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    MJCP's Avatar
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    Duraleigh,
    You are correct, my leak is evident while the pump runs, I was only suggesting that a hard to find leak may be somewhere on the other side of the pump that they may not have looked for, and possibly missed.
    15x32 Lazy L Inground / Concrete - 25,000 US Gal 1979 build
    1.5Hp/ Sand Filter, 7th season with Pool
    Painted cement finish repainted 2011
    BROMINE - (Purchased Home that way) Bleach shock
    400,000 btu Pentair Master Temp NG

  15. Back To Top    #15

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    What's confusing me is the terminology.

    A suction side leak results in air bubbles in the pump basket and possibly priming issues, but not in water loss, unless it's below water level.
    A pressure side leak results in rapid water loss, especially when the pump is on. Also, as has been suggested already, air entering the system and filling cavities such as heaters and filters.

    Bubbles coming out of the return line is always a suction side issue because with the pump running, anything after the pump is under pressure and will result in water spraying out, not drawing air in (unless there is a venturi such as is used with an ozone generator, or hydrotherapy jet).

    Are you losing water or is the issue just bubbles returning to the pool?
    If you're not loosing water, it's probably a suction leak above ground and in the valves and/or fittings and glue joints right before the pump. Check a little and seldom checked drain plug on the bottom of the pump's hair and lint trap.

    I use the wet dish towel trick to detect suction side leaks. Wrap a dripping wet towel around the glue joints, fittings, and valve joints, one at a time until the bubbles subside.
    Sean Assam - Sean@teamhorner.com
    National Accounts and Commercial Products Manager
    AquaCal Heat Pumps www.aquacal.com
    AutoPilot Salt Chlorine Generators www.autopilot.com

  16. Back To Top    #16

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    I have to reply to this because I had bubbles in my return line and DID have a pressure side leak, right at the pool return. (It is still there, I'm working up to doing the work to fix it). I found the leak by pressure testing my returns, the shallow line was fine, the deep end line leaked. I confirmed that this is where the leak was (and is) by blocking off that return line - no leak since! And I was losing significant amounts of water (1" or more per day), so there is no question that I have found the leak.

    There is a thread from last year that I started and will revive once I fix the leak. Despite being very counter-intuitive, you can definitely get bubbles in the return from a pressure side leak!
    20 x 40 vinyl IG. SWG. Solar. Ikeric VS pump.

  17. Back To Top    #17

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    tphaggerty,

    I understand what you're describing.

    If you've blocked off the water at the equipment side, it's in your line somewhere. That would not explain why air is blowing into your pool though.

    However, after extensive and indepth logical calculations...
    if you've blocked off the water at the wall return, your leak may be right at the return eyeball fitting and may be causing a venturi action, drawing in air when the pump is on, but leaking with the pump off. The test plug may be just at the point of blocking the leak and may not be too deep into your return. If it were deeper than at the return, you would still have a leak.

    I'm very interested in hearing where the leak finally is found. Please keep us (me) posted!
    Sean Assam - Sean@teamhorner.com
    National Accounts and Commercial Products Manager
    AquaCal Heat Pumps www.aquacal.com
    AutoPilot Salt Chlorine Generators www.autopilot.com

  18. Back To Top    #18

    Re: Possibly???

    Quote Originally Posted by MJCP
    Most everyone here is a better source than me, but I thought I would share my experience in case it helps.

    The "air always comes from the suction side" has always puzzled me.

    I have a known leak in my heater (I'll fix it after my Daughters pool party this weekend). I believe that would not be the suction side. Yet every time the system is turned off, this leak "becomes" the suction side. I can hear it sucking as it is in a fitting right by the shutoff switch. It fills the heater, and filter with air, even the pump basket ends up empty by the time I turn it back on. Then when fired back up I have Air in the lines.

    So maybe you also have a Leak in the parts of the system you haven't checked yet, and it only "becomes" the suction side after it is turned off for a while.
    MJ:

    I have always assumed that air in the return lines to the pool has to be a suction side leak. I still have not located the source so maybe I should check the pressure side.
    Mike
    20,000 gallon in-ground gunite with attached spa
    Pentair Cartridge Filter
    3/4 hp Sta-Rite Pump
    2 hp Whisperflo Spa Pump
    Ray-Vac cleaner

  19. Back To Top    #19
    Quote Originally Posted by Poolsean
    What's confusing me is the terminology.

    A suction side leak results in air bubbles in the pump basket and possibly priming issues, but not in water loss, unless it's below water level.
    A pressure side leak results in rapid water loss, especially when the pump is on. Also, as has been suggested already, air entering the system and filling cavities such as heaters and filters.

    Bubbles coming out of the return line is always a suction side issue because with the pump running, anything after the pump is under pressure and will result in water spraying out, not drawing air in (unless there is a venturi such as is used with an ozone generator, or hydrotherapy jet).

    Are you losing water or is the issue just bubbles returning to the pool?
    If you're not loosing water, it's probably a suction leak above ground and in the valves and/or fittings and glue joints right before the pump. Check a little and seldom checked drain plug on the bottom of the pump's hair and lint trap.

    I use the wet dish towel trick to detect suction side leaks. Wrap a dripping wet towel around the glue joints, fittings, and valve joints, one at a time until the bubbles subside.
    Sean:

    I am not noticing any significant water loss just the air spurts in the return lines to the pool. I have wrapped each connection with adhesive rubber tape (that is what sealed my first leak two years ago) and I am still getting air back through the returns. I have not yet taken apart the jandy valves to see if those could be a source of air sucking in. With the way they are screwed down, it would not seem likely that air could enter although if the gasket is bad I guess that it could.
    Mike
    20,000 gallon in-ground gunite with attached spa
    Pentair Cartridge Filter
    3/4 hp Sta-Rite Pump
    2 hp Whisperflo Spa Pump
    Ray-Vac cleaner

  20. Back To Top    #20

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    Check the grease fitting on the Jandy valve. Sometimes these get broken off and allow air to draw in. Did you check the bottom drain plug on your pump trap?
    Sean Assam - Sean@teamhorner.com
    National Accounts and Commercial Products Manager
    AquaCal Heat Pumps www.aquacal.com
    AutoPilot Salt Chlorine Generators www.autopilot.com

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