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Thread: To aerate or not to aerate, that is the discussion.

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    To aerate or not to aerate, that is the discussion.

    Split from Acid Aeration .

    Quote Originally Posted by mas985 View Post
    You don't have to use an aerator. It just speeds things up. The PH will usually rise on it's own, albeit slowly, with just normal pool activity.

    I have very high TA fill water and am constantly fighting high TA and high PH but I don't bother with aeration because it is futile. I just keep PH at the lower end of the range and the CSI slightly negative and TA comes down on it's own and settles in a range around 90-100 ppm.
    @mas985

    I respectfully disagree with your assertion that aeration is futile. pH rises faster with aeration than without. I have lots of aeration in my pool (sheer spillway from spa and rock waterfall) and it has a definite impact on pH

    Also, @lynzizzle lives in Indiana and her swimming season is coming to a close very soon. She doesn't have the luxury of a 10 month swim season that us westerners have and so she would definitely benefit greatly from some additional aeration equipment, if not this swim season than definitely next.

    Her high TA coupled with her high pH means that her pool water will always be very alkaline. That can cause eye irritation and affect the aesthetic properties of her water as well as make calcium scaling more of an issue. She should definitely consider acid/aeration treatments above and beyond her baseline pool water care regimen as a way to improve her pool water quality. I guarantee she would feel the difference swimming on a nominal 7.4 pH low alkalinity pool in comparison to her normally higher pH pool water.



    Last edited by zea3; 09-05-2014 at 04:52 PM. Reason: split posts to a new thread

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    Re: Acid Aeration

    Quote Originally Posted by SunnyOptimism View Post
    I respectfully disagree with your assertion that aeration is futile. pH rises faster with aeration than without. I have lots of aeration in my pool (sheer spillway from spa and rock waterfall) and it has a definite impact on pH
    You misunderstood my comment. I am not saying aeration doesn't work, it does. I meant it is futile for me to aerate because I would be constantly aerating. My TA rises so quickly with high TA fill water, as soon as I lower TA, it is back up again very quickly. I find it is easier to live with the higher TA levels than it is to be constantly battling with it.

    So instead of focusing of PH and TA, I now target a CSI of -0.5 and let PH and TA take care of themselves. I am able to keep TA within 90-100 ppm by just keeping the PH close to 7.2. That compensates for the high TA fill water being added every day.
    Mark
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    Acid Aeration

    Quote Originally Posted by mas985 View Post
    You misunderstood my comment. I am not saying aeration doesn't work, it does. I meant it is futile for me to aerate because I would be constantly aerating. My TA rises so quickly with high TA fill water, as soon as I lower TA, it is back up again very quickly. I find it is easier to live with the higher TA levels than it is to be constantly battling with it.

    So instead of focusing of PH and TA, I now target a CSI of -0.5 and let PH and TA take care of themselves.
    Ah, understood! No harm, no foul ....

    Any waterfalls, sheer descents or spillways?

    One method I used to drop my TA FAST was to acid/aerate my spa water (~ 1000 gal) with the spillway off, then dump it into the pool and repeat.

    I got a 150ppm TA pool down to ~ 80 ppm in two days [EDIT - I double checked my pool diary, it was a long weekend so more like 4 days of acid/aeration/dump from the spa]. Of course, my fill water is 90ppm so it's not a major contributor to TA.



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    Re: Acid Aeration

    I do have a spillover that is run about 1/2 hour per day but only 3" above the water level and an SWG which helps with aeration. I also have a DIY automatic dosing system that adds 2 gallons of acid per month at peak.

    But even a pool with no extra aeration will naturally aerate, just much slower. The rate of aeration is related to the air/water boundary and external aeration just increases this boundary surface area so it occurs much faster.

    So any pool with high TA and a target low PH (7-7.2), over time the TA will gradually drop without external aeration. However, at some point, the TA will stabilize and there isn't much point in trying to go below this stabilized point because you would need to have a lower PH target and that could be risky but still possible as long CSI isn't too low.
    Mark
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    Re: Acid Aeration

    Quote Originally Posted by mas985 View Post
    I do have a spillover that is run about 1/2 hour per day but only 3" above the water level and an SWG which helps with aeration. I also have a DIY automatic dosing system that adds 2 gallons of acid per month at peak.

    But even a pool with no extra aeration will naturally aerate, just much slower. The rate of aeration is related to the air/water boundary and external aeration just increases this boundary surface area so it occurs much faster.

    So any pool with high TA and a target low PH (7-7.2), over time the TA will gradually drop without external aeration. However, at some point, the TA will stabilize and there isn't much point in trying to go below this stabilized point because you would need to have a lower PH target and that could be risky but still possible as long CSI isn't too low.
    @mas985

    Let's ask the moderators to remove our conversation thread here starting back with some of my earlier disagreements. I don't 100% agree with some of your points above as I think you're talking about the dynamic equilibrium properties of your water and I'm more thinking along the lines of transient equilibrium effects by using a greater number of acid/aeration cycles.

    @modsquad - work your surgical magic!!



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    To aerate or not to aerate, that is the discussion.

    @mas985

    Perhaps I am misunderstanding you again (if so, I apologize for being tedious) but this is the statement that I disagree with -

    However, at some point, the TA will stabilize and there isn't much point in trying to go below this stabilized point because you would need to have a lower PH target...
    I believe this is only true in the steady state equilibrium case where you set your pH to a low value and then the TA simply drifts to its equilibrium value for whatever amount of CO2 out gassing naturally occurs.

    If you use rapid-enough acid/aeration cycling, you can drop your TA to almost any value you have the time and patience to get to. That assumes, of course, you turn off any high-TA source of fill water.

    I do believe that TA has a pH dependency to it, that is, there is an equilibrium value of carbonate alkalinity for a given pH. That would be the lower limit of alkalinity which can be achieved by cycling water with acid and aeration, but I'm not sure what that is (ChemGeek could easily tell us that) and I'd bet it's pretty darn low (like a few ppm not tens of ppm).

    Anyway, my point is that AA cycling can push your TA down as far as you'd like it to go.



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    Re: To aerate or not to aerate, that is the discussion.

    I agree that TA can be lowered to any point fairly quickly but that was not my point. I am looking at this from an overall pool management perspective. For pools with high TA fill water and high evaporation as I experience and probably you too, TA lowered with acid/aeration cycles won't stay there very long unless it is either a constant or a periodic process. Also adding extra aeration increases evaporation and that requires adding high TA fill water back to the pool which is self defeating. Especially rigs that spray water into the air. To achieve stable TA, every time TA is added to the pool, it must be removed with acid and CO2 out gassing. The real question is how to achieve this with the least amount of work.

    So my main point is that for high TA fill water pools, like mine and the OP's, if you can keep the PH and TA in a reasonable range and still maintain a slightly negative CSI without adding extra aeration (and evaporation), I think you are better of in the long run. My solution was an acid injection system and keeping PH at a fairly low level (~7.2). Over time, this results in a stable TA level that is in the upper range but still with a slightly negative CSI which keeps scale off the SWG and tile. And because of the increase evaporation caused by extra aeration, I believe my method also uses less acid over the long haul not to mention that it saves on water too! Just think of this as a long and drawn out method of lowering TA (actually keeping TA low) that never ends.

    I was just trying to give the OP an alternative method. The path they are on now, is going to lead to endless cycles of lowering TA. Life is way too short for that.
    Mark
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    Re: To aerate or not to aerate, that is the discussion.

    Gotcha! Thanks for the detailed thoughts.

    Are you on a well?

    My water is from a municipal source (Tucson Water) and the TA is not bad at all, about 90ppm out of the hose.





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    Re: To aerate or not to aerate, that is the discussion.

    My city fill water TA is around 250. This year hasnt been too bad because I havent had to fill many times because the rain has replenished what has evaporated. My TA is 100 right now and evertime I fill an inch I add 3.6ppm of TA. Everytime I add acid it takes away the 3ppm that the city water put in so basically its back and forth. I have a very small waterfall that pushes the pH up also. Right now I have to add acid about every 3 days to drop 0.2.

    If I was to lower the TA to 80 then an inch of city fill would add 4.1 ppm so the lower you go the more the fill adds. Its a pay now or pay later kind of deal. As long as mine is 80-100 I dont worry about it but anything much over that and I believe I would aerate. You just have to pick how many days in between acid additions you want to deal with.
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    Re: To aerate or not to aerate, that is the discussion.

    Quote Originally Posted by SunnyOptimism View Post
    Are you on a well?
    The city uses a lot of aquifers so basically wells. They have surface water too but since we are in a drought, they are using the wells a lot more. Another reason, I am trying to manage evaporation.
    Mark
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    Re: To aerate or not to aerate, that is the discussion.

    When I have the time, I have an area on my property that could hold a 500 gal rain water cistern. I'd love to collect and do some partial filling with that as we get hammered with CH here. My fill water CH is never below 280ppm and my pool this season was constantly at 450ppm.

    I'm also likely to be investing in some salt blasting equipment so I can do my own descaling on the tile.....



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    Re: To aerate or not to aerate, that is the discussion.

    Just to clarify what Mark's been talking about, it's steady-state equilibrium. There is still outgassing going on and that causes the pH to rise and he is adding acid to keep the pH lower. The net result is that this would have the TA drop at a certain rate, but because of the fill water that is adding TA from evaporation and refill, there is a point of stability in the TA level where the rate of TA drop from the acid addition equals the rate of TA rise from the evaporation/refill.

    ACTIVITY . pH . TA
    Outgassing . + ... 0
    Acid ........... - .... -
    Evap/Refill .. 0 .... + (may affect pH, but for simplicity I assume it doesn't)
    ------------------------
    NET ............ 0 .... 0
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    To aerate or not to aerate, that is the discussion.

    I suppose this just entertaining fantasies here but ... for high TA fill water couldn't one use a strong base anion exchange resin in a setup similar to a home water softener in order to remove carbonates. The SBA resins act like their softener counterparts by exchanging -OH anion for (-2)CO3 anion (I believe there are chloride versions too). Regeneration is done via a strong base rinse cycle (aqueous sodium hydroxide). Fill water would then be a higher pH necessitating an additional acid neutralizing step.

    ....I wonder what that would cost....



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    Re: To aerate or not to aerate, that is the discussion.

    Yes, that would work but it's far less common to find than the cation exchange resins used to reduce water hardness.
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