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Thread: SWG Start-up Observations

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    ktdave's Avatar
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    SWG Start-up Observations

    I fired up my SWG (Pentair Intellichlor IC-20) for the first time yesterday and noticed that while it was running, bubbles were effervescing out of all the returns. I know this has been discussed here in the past, but I was under the impression that these bubbles were supposedly so small that they were hardly noticeable. These bubbles are quite evident, much like you would see in a clear glass when pouring a can of sprite into it. I just wanted to refresh the discussion with my observations.

    Not that I'm worried that anything is wrong, just would like to hear other's experience.
    11,000 gal. gunite w/midnight blue and white pearl PebbleTec
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    JasonLion's Avatar
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    I have an AutoPilot and the bubbles are quite small and very difficult to see, the sun has to be at just the right angle.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    TFP Guide

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    Ditto for here, if you ares not sitting at the exact angle, I find you cant tell when its producing.

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    When I first fired up my IG20 there was a lot of fine white bubbles that came out, almost cloudlike. After a few hours it cleared up. I do see fine bubbles
    mostly at night in front of the lights where the returns are when the SWG is on, I believe this is normal. Its hard to spot in direct sunlight.

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    ktdave's Avatar
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    Could water temp be a factor. I'm in the houston area where my water temp is 84-88.

    It also might be more apparent due to my dark pebble finish.
    11,000 gal. gunite w/midnight blue and white pearl PebbleTec
    Intelliflo 4x160 pump
    Intellichlor IC-20 SWG
    Pentair cartridge filter 420 sq. ft.
    Mastertemp 400K BTU heater
    Legend Platinum cleaner
    Pool School
    JasonLion's Pool Calculator
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    SWG Start-up Observations

    My limited experience.

    GlodLine SWG. I have a fairly dark finish. The bubbles are very obvious when the SWG is on. I can see them from 25 feet away at my back door, thats on way I check that all is good in my pool.

    50 minutes later they are not there. (mine is set at 50 % ).
    14,500 inground gunite
    7' connected spa with overflow waterfall
    Goldline salt water chlorine generator
    Hayward 4 cartridge filter
    Hayward 400K heater
    Completed January 07

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    I've never noticed any bubbles. I know the SWCG is working properly because it easily maintains the chlorine level.

    I'm feeling left out....

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    Re: SWG Start-up Observations

    Quote Originally Posted by vegas_dp
    My limited experience.

    GlodLine SWG. I have a fairly dark finish. The bubbles are very obvious when the SWG is on. I can see them from 25 feet away at my back door, thats on way I check that all is good in my pool.

    50 minutes later they are not there. (mine is set at 50 % ).
    That is exactly my experience.
    11,000 gal. gunite w/midnight blue and white pearl PebbleTec
    Intelliflo 4x160 pump
    Intellichlor IC-20 SWG
    Pentair cartridge filter 420 sq. ft.
    Mastertemp 400K BTU heater
    Legend Platinum cleaner
    Pool School
    JasonLion's Pool Calculator
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    Just today, I was at a pool (one of the lines is leaking ) and the homeowner reiterated his complaint about the new filter we installed this spring (last year we installed a SWCG and DE filter - this year he BEGGED us to install a cart filter, the DE was too much work) - "ever since the new filter was installed, I get air bubbles out of my returns, and it never happened before")

    Now, in the process of finding the leak, we've pressure tested the lines (found the leaking one ) and there is NO air entering the system! However, we did see the bubbles comming out of the returns every minute or so ... hmmmm. It finally dawned on me that it might be hydrogen from the SWCG, but the bubbles were huge I turned off the SWCG, and the bubbles stopped. All I can assume is that there is a '90' somewhere in the line that collects the released hydrogen and when the 'pocket' gets large enough, the big bubbles are entrained into the return water. *this is not a pool we built, so the plumbing is ~ unknown, but on our pools we never see the bubbles -even the small ones- because we have 8 - 12 returns on our pools and I speculate that the bubbles are evenly distributed and thereby aren't concentrated enough to be noticeable from any one return*

    Just a little 'field report' from waste
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    ktdave's Avatar
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    Thanks for the insight Ted! I do have my fair share of 90's at the pad. That could well be a contributing factor.
    11,000 gal. gunite w/midnight blue and white pearl PebbleTec
    Intelliflo 4x160 pump
    Intellichlor IC-20 SWG
    Pentair cartridge filter 420 sq. ft.
    Mastertemp 400K BTU heater
    Legend Platinum cleaner
    Pool School
    JasonLion's Pool Calculator
    TF Test Kits

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    Re: SWG Start-up Observations

    Quote Originally Posted by ktdave
    Quote Originally Posted by vegas_dp
    My limited experience.

    GlodLine SWG. I have a fairly dark finish. The bubbles are very obvious when the SWG is on. I can see them from 25 feet away at my back door, thats on way I check that all is good in my pool.

    50 minutes later they are not there. (mine is set at 50 % ).
    That is exactly my experience.
    Same here. It doesn't bother me as I can tell at a glance when the SWG is active.

    I, too, have several 90s in the return path, so that sounds like a plausible explanation for the bubbles. Are they hydrogen? It would be interesting to collect them to see like I did in chemistry class many years ago.
    blubluenoiseise

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    When I run the pump on high speed you can't really see the bubbles. On low speed the bubbles are apparent on the return closest to equipment. Some 1/8" size and very small bubbles.
    IG 18x36 oval vinyl, Spill over spa, Northstar 2hp-2spd, 2.5" piping, S310T 500lb Sand filter, 400k gas heater, AutoPilot SWCG
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    Quote Originally Posted by Gimpy
    I've never noticed any bubbles. I know the SWCG is working properly because it easily maintains the chlorine level.

    I'm feeling left out....
    Run your pump and SWG at night and turn on an interior pool light (or shine a light towards the returns). They should be quite visible then. It does seem that in daylight it takes a darker pool surface to see the bubbles more clearly (or the sun at the right angle).

    And yes, these are hydrogen gas bubbles. Collect them in a jar (hydrogen is lighter than air so keep the mouth of the jar pointed down, then cap it), light a match, open the jar, and boom. Actually, more like a small pop or crackle.

    It's these hydrogen gas bubbles that aerate the water, causing carbon dioxide to get outgassed which makes the pH rise.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
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    Quote Originally Posted by chem geek
    Run your pump and SWG at night and turn on an interior pool light (or shine a light towards the returns). They should be quite visible then. It does seem that in daylight it takes a darker pool surface to see the bubbles more clearly (or the sun at the right angle).

    And yes, these are hydrogen gas bubbles. Collect them in a jar (hydrogen is lighter than air so keep the mouth of the jar pointed down, then cap it), light a match, open the jar, and boom. Actually, more like a small pop or crackle.

    It's these hydrogen gas bubbles that aerate the water, causing carbon dioxide to get outgassed which makes the pH rise.
    Richard, - a question: How does the O2 get 'used up'? In other words, since electrolysis of water releases 1 H and 2 O's, we would see both as bubbles, but in the salt water/chlorine generation, only hydrogen bubbles are seen, which should mean that the oxygen is being used for chlorine production. I am curious, I think, as to what the equations are.
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    Oxygen gas comes out when the disinfecting chlorine gets used up. This post lists the various chemical reactions.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    The link Jason pointed to has the chemical reactions. In words, I would say that while hydrogen gas is produced at one plate during the electrolysis, chlorine gas (from the chloride ions -- that is, salt) is produced at the other plate -- oxygen gas is not produced there (at least not very much). The chlorine gas dissolves in water to produce hypochlorous acid (and hydrochloric acid). Eventually, when the hypochlorous acid (which is what we call disinfecting chlorine) gets used up, it releases oxygen. So in some sense you can consider that the chlorine is a strong intermediate oxidizer on the way towards producing oxygen.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
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