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Thread: SUCTION-LIMITING VENT SYSTEM (Atmospheric Vent) is blowing water???

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    SUCTION-LIMITING VENT SYSTEM (Atmospheric Vent) is blowing water???

    I just took on a pool built in the late 1980's. It has a (field built) atmospheric vent that is blowing water, draining the pool when the pump runs. Does anybody know what would cause this? How to cure this? Here is an extract I found on the net addressing such vents:
    II) SUCTION-LIMITING VENT SYSTEM - A suction-limiting vent system with a tamperresistant atmospheric opening.
    Staff interpretation: A suction-limiting vent system is also called an atmospheric
    vent. It is a pipe teed to the suction side of the circulation system on one end and
    open to the atmosphere on the opposite end. The pipe is normally full of water
    equal to the same height as the pool. When a blockage occurs at the main drain,
    air is introduced into the suction line thus causing the pump to lose prime and
    relieving the suction forces at the main drain (suction outlet).

    Source: http://www.aandlpoolservice.com/news.html

    Any ideas?

    Thanks, Scott

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    Patrick_B's Avatar
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    Re: SUCTION-LIMITING VENT SYSTEM (Atmospheric Vent) is blowing water???

    Welcome to the forum.

    I'm sorry but I don't have an answer for you.
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    Mod Squad Bama Rambler's Avatar
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    Re: SUCTION-LIMITING VENT SYSTEM (Atmospheric Vent) is blowing water???

    If what you're seeing is a suction limiting vent and it's installed correctly there's no way for it to blow water out of it. It should be plumbed into the suction side of the pump and therefore would never see pressure above the level of the pool.

    It sounds like it's plumbed on the discharge side of the pump and therefore isn't a suction limiting vent at all.

    Can you post a picture of it?
    Dave J. TFP Moderator
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    Re: SUCTION-LIMITING VENT SYSTEM (Atmospheric Vent) is blowing water???


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    Re: SUCTION-LIMITING VENT SYSTEM (Atmospheric Vent) is blowing water???

    This pool has several distinguishing features. It has 10 floor returns fed by an A&A 5 Port Top feed valve head. I thought the vent was somehow tied to the A&A valve for ventilation/water (return) balancing reasons. I called A&A in AZ yesterday and they said there is no design requirement with their valve that would necessitate such a ventilation device. Sooo, I am left to conclude this is an atmospheric vent???? What elese might this be? It is not tied to the sewer/backwash line. I removed the sight glass from the backwash line and plugged the bottom of the slide valve so there is absolutely no water pumping out of the system. The vent only spews water when the pump is on.

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    JasonLion's Avatar
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    Re: SUCTION-LIMITING VENT SYSTEM (Atmospheric Vent) is blowing water???

    Do you have a spa, or part of the pool with spa like jets? Spa jets typically have an air intake pipe so the jets come out mixed with air.

    Nothing else I can think of makes any sense.
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    Re: SUCTION-LIMITING VENT SYSTEM (Atmospheric Vent) is blowing water???

    No spa. I'm thinking of taking the lid off the pot, and sending water down the vent pipe to blow out possible debris?

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    mas985's Avatar
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    Re: SUCTION-LIMITING VENT SYSTEM (Atmospheric Vent) is blowing water???

    Cleaning it might help. Did it always do this or did it just start doing this? Have you tried cleaning the filter? Does the pool have any jets?
    Mark
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    Re: SUCTION-LIMITING VENT SYSTEM (Atmospheric Vent) is blowing water???

    Quote Originally Posted by mas985 View Post
    Cleaning it might help. Did it always do this or did it just start doing this? Have you tried cleaning the filter? Does the pool have any jets?
    I noticed this after I cleaned the filter 2 days ago. 10 floor returns fed by five 1.5" lines plugged into the A&A 5 port valve head. There is one (1) eyeball/surface return in the wall, by the steps. It may have fed a pressure cleaner in the past. Odd thing is, only 2 return lines split out from the filter. One line feeds the 5 port and the other line feeds the one eyeball/surface return. When I turn the diverter valve and shut off return flow to the 5 port line, the vents stops blowing water???

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    mas985's Avatar
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    Re: SUCTION-LIMITING VENT SYSTEM (Atmospheric Vent) is blowing water???

    What happens when you turn off the single return and have only the in-floors? More or less water?

    Are any of the in-floor returns close to the main drain and is the water coming out of the vent periodic?
    Mark
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    Re: SUCTION-LIMITING VENT SYSTEM (Atmospheric Vent) is blowing water???

    It's 15 degrees this morning. I plugged the vent and wrapped it in plastic and heavy towels and placed a box over it last night. This allowed me to restore (complete) circulation to the pool in advance of the hard freeze we are experiencing. I believe the water that was coming out of the vent should not pose a (pressurized) concern now that the water is blocked from coming out. The water should find its way back into the circulation system without ant detrimental effects. If there are no observable consequences form plugging the vent I may wait until warmer weather, or just leave it be. Your thoughts? Everybody's thoughts???? Thanks!

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    Mod Squad Bama Rambler's Avatar
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    Re: SUCTION-LIMITING VENT SYSTEM (Atmospheric Vent) is blowing water???

    I certainly wouldn't leave it plugged if it turns out to be a suction vent (though I'm not sure it is a suction vent,). You don't want that liability.

    I think I'd work on finding out what it is and then decide whether to leave it plugged or not.
    Dave J. TFP Moderator
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