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Thread: Is there a certain window of time

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  1. #1
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    Default Re: Is there a certain window of time

    But is it the aerating that's lowering the alk, or the acid?

    In other words, is it-

    1- PH is 8, Alk is 200. Add acid, PH drops to 7.2, alk at 200, aerate, alk drops while ph rises. Keep lower PH and aerating until alk lowers to where you want it then stop.

    2- PH is 8, Alk is 200. Add acid, PH drops to 7.2, alk drops to 140. Aerate, PH rises but alk stays at 140 because carbon dioxide is gassing off from aeration. Continue to drop PH and aerate until you get alk where you want it.

    I had understood it to be #2. However, My PH is dropping, but alk isn't. And for some reason Alk increases along with PH when aerating.

    Somethings not right

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    Default Re: Is there a certain window of time

    Can anyone help?

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    Tredge is offline Registered+ Thread Analyst Tredge 0
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    Default Re: Is there a certain window of time

    I'm also dealing with a high TA.

    Are you also adding CYA? I think this will make it look like your TA and PH are going up when they are not.

    Aerating actually causes your PH to go up. The only way Aerating will work is to keep adding Acid....if you can keep the PH low for a period of time then the TA WILL drop. It can take weeks.

    Shoot for a constant PH of 7.0 (6.8 for a plaster pool) and watch your TA closely. When it starts to drop it will drop significantly.
    Also remember that TA isnt a thing, its a measurement of the waters resistance to changing PH. It can go back up and in my experience will bounce around a little while you are trying to stabalize the PH.

    This is all from info I've gleamed out of this forum, I'm still working on it myself.
    Last edited by Tredge; 06-22-2006 at 12:04 PM.
    Some people have hobbies.....I have a pool.

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    Default Re: Is there a certain window of time

    Quote Originally Posted by Tredge
    I'm also dealing with a high TA.

    Are you also adding CYA? I think this will make it look like your TA and PH are going up when they are not.
    Nope, only using bleach. CYA is about 20ish and holding.

    Aerating actually causes your PH to go up. The only way Aerating will work is to keep adding Acid....if you can keep the PH low for a period of time then the TA WILL drop. It can take weeks.

    Shoot for a constant PH of 7.0 (6.8 for a plaster pool) and watch your TA closely. When it starts to drop it will drop significantly.
    Also remember that TA isnt a thing, its a measurement of the waters resistance to changing PH. It can go back up and in my experience will bounce around a little while you are trying to stabalize the PH.
    I had to add 3" of water to make up for evaporative loss last night. Since my fill water is highly alkaline and lower PH than my pool, I waited until it was circulated and retested. PH was down, Alk was 190.

    The Alk number doesn't bother me (vinyl liner), but the PH tends to shoot back up within days, so I'd like to get it down to 100 or so and see if my PH stays more stable. Water clarity and feel is much better when I keep the PH between 7.2-7.6 ish.

    I set up my sump pump to aerate, but we have a good chance at thunderstorms today so I'm waiting to add acid and start aerating until I see what the rain does to the water. If it doesn't have much affect or misses us again, I plan to attack the alk daily until it drops to where I want it.

    This is all from info I've gleamed out of this forum, I'm still working on it myself.
    Thanks. I try to read as much as possible before asking questions, but this one has been stumping me. I'm starting to think it's primarily the high starting alk that is making it so hard to keep alk down permanently (ie, without adding fill water). Once alk is lowered and properly aerated, it shouldn't rise sharply, right?

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    Tredge is offline Registered+ Thread Analyst Tredge 0
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    Default Re: Is there a certain window of time

    Higher Alkalinity means a more stable PH, lowering the TA means the PH will actually be less stable.

    I have the same trouble you do with Fill water....it will always creep up when you have to replace from evaporation.....although slowly.

    My plan is to get the TA down to somthing reasonable so that I can get a stable PH....then forget about the TA and Stop aerating.

    Remeber that aerating will raise your PH. If you have a PH you like, then Stop aerating and dont worry too much about the Alkalinity.

    Unless you have a problem with scaling I would forget about trying to "fix" the TA because your fill water will mean a constant battle....you'll never get it to stick at a low number.

    No matter what you do you'll probably always have to add Acid....the good news is that your PH should stay fairly steady compared to other pools. The High TA doesnt cause the PH to shoot up....thats another problem and may be related to your TA increasing on you.

    Once alk is lowered and properly aerated, it shouldn't rise sharply, right?
    Thats my understanding from the technical explanations yes...but I have seen it bounce around a bit, I always attributed it to my testing or other factors.
    Last edited by Tredge; 06-22-2006 at 02:42 PM.
    Some people have hobbies.....I have a pool.

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    Default Re: Is there a certain window of time

    Quote Originally Posted by Tredge
    Higher Alkalinity means a more stable PH, lowering the TA means the PH will actually be less stable.
    That's what I understood. However when I get my PH down to 7.2, it's back up to over 8 within a week. Perhaps that's just part of the BBB method, and I should just be happy to acid each week to knock it back down?

    I have the same trouble you do with Fill water....it will always creep up when you have to replace from evaporation.....although slowly.
    Mine seems to shoot up as fast as the PH does.

    My plan is to get the TA down to somthing reasonable so that I can get a stable PH....then forget about the TA and Stop aerating.
    Mine too, but it's not working very well

    Remeber that aerating will raise your PH. If you have a PH you like, then Stop aerating and dont worry too much about the Alkalinity.
    When I do this, the PH continues to shoot up. It's hard to stop aerating when cannon balls are so much fun That's why I started this thread. It seems like just swimming and general splashing around is causing the PH to climb. Since the alk climbs with it, I figured I'm not doing a good enough job aerating, and the carbon dioxide formed from lowering the PH is being re-converted to whatever instead of gassing off, giving me the increased alkalinity reading.

    Unless you have a problem with scaling I would forget about trying to "fix" the TA because your fill water will mean a constant battle....you'll never get it to stick at a low number.
    My grand vision was to get the alk down, then as I have to add an inch or two of fill water, I can easily beat it back down. Do you think this is futile?

    No matter what you do you'll probably always have to add Acid....the good news is that your PH should stay fairly steady compared to other pools. The High TA doesnt cause the PH to shoot up....thats another problem and may be related to your TA increasing on you.
    If my PH would remain stable, I wouldn't give the alk a second thought. Whats the other problem you mention in your last sentence?

    Thats my understanding from the technical explanations yes...but I have seen it bounce around a bit, I always attributed it to my testing or other factors.
    I've tried to be as precise and consistent as possible in my testing, but it's possible I'm getting bad readings, I guess.

    Thanks a bunch for the input

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    Default Re: Is there a certain window of time

    I forgot to add above-

    Looks like the rain has a great chance of missing us again, so when I was home this noon I tested again.

    PH- 7.8, up .2 from yesterday
    Alk- 190

    I added the acid to knock PH down to 7.0, and set up my sump pump with a hose returning to the pool to aerate. First time I've done it this way. I also plan to do some serious splashing about this evening

    I'll retest in the am, and assuming alk has dropped, will knock ph back down and continue daily as needed.

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    waterbear is offline Lifetime Member Sniggle Mechanic waterbear 4 stars waterbear 4 stars waterbear 4 stars waterbear 4 stars
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    Default Re: Is there a certain window of time

    Quote Originally Posted by Rangeball
    But is it the aerating that's lowering the alk, or the acid?
    TA is a measure of the carbonic acid/bicarbonate/carbonate buffer system in the water. Only the carbonate/bicarbonate part of it is measurable by testing. When you lower pH you shift the amounts of the three components to more carbonic acid and less of the other two. The amount of the buffer is unchanged. When you aerate you drive off some of the carbon dioxide (carbonic acid is just carbon dioxide gas dissolved in water....think club soda, exactly the same thing. Aerating...think shaking the bottle of club soda to make it go flat...exactly the same thing).
    By driveing off the carbon dioxide you:
    1 lower the amount of the buffer system in the water
    2 this causes the pH to rise since there is a higher ratio of bicarbonate/carbonate to carbonic acid and less acid means higher pH (simplified a bit but essentially true)
    3. once the pH rises the buffer system reaches a new equilibrium point and there will be less meaurable carbonates/bicarbonates in the water....you have now succesfully lowered the TA!

    In other words, is it-

    1- PH is 8, Alk is 200. Add acid, PH drops to 7.2, alk at 200, aerate, alk drops while ph rises. Keep lower PH and aerating until alk lowers to where you want it then stop.

    2- PH is 8, Alk is 200. Add acid, PH drops to 7.2, alk drops to 140. Aerate, PH rises but alk stays at 140 because carbon dioxide is gassing off from aeration. Continue to drop PH and aerate until you get alk where you want it.

    I had understood it to be #2. However, My PH is dropping, but alk isn't. And for some reason Alk increases along with PH when aerating.
    Since the measured TA is dependant on the pH at which it is measured you might see this effect. If you measure the ALK at a pH of, say 7.8, and follow the procedure and then retest once the pH is back at 7.8 you will find that the measured TA is now lower. IF the TA is very high you need to keep the pH low as you aerate and keep adding acid to keep it low and also monitor the TA. You will see it start to decrease. When it has lowered then stop adding acid and aerate until the pH is where you want it, say 7.4. Your TA might read slightly lower at this point or not. The lower you can safely get the pH to and keep it there while you aerate the faster you will lower the TA in the water since you will maximize the amount of the buffer that is in the form of carbonic acid.

    Somethings not right
    Hope this doesn't confuse you too much!
    Retired pool store and commercial pool maintenance guy.

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    Default Re: Is there a certain window of time

    Quote Originally Posted by waterbear
    Since the measured TA is dependant on the pH at which it is measured you might see this effect. If you measure the ALK at a pH of, say 7.8, and follow the procedure and then retest once the pH is back at 7.8 you will find that the measured TA is now lower. IF the TA is very high you need to keep the pH low as you aerate and keep adding acid to keep it low and also monitor the TA. You will see it start to decrease. When it has lowered then stop adding acid and aerate until the pH is where you want it, say 7.4. Your TA might read slightly lower at this point or not. The lower you can safely get the pH to and keep it there while you aerate the faster you will lower the TA in the water since you will maximize the amount of the buffer that is in the form of carbonic acid.

    Hope this doesn't confuse you too much!
    I believe I understood everything, and I believe I am following the procedure as outlined, what I don't understand is why I'm NOT seeing a signficant PH/ALK drop when I add the required amount of acid and aerate. Any ideas?

    The only variable seems to be aerating WHILE trying to get the PH to drop, but I've eliminated this, so we'll see.

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    Default Re: Is there a certain window of time

    Tested PH at noon-

    7.3, down from the 7.6 I got this morning. I plan to get more acid, and lower it until I have a 7.0 reading. At that time I'll retest ALK and start aerating again.

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