Is there a certain window of time

To aerate when lowering alkalinity?

My fill water is high alk. Tests at 320. 3 times this year I've added acid and tried to lower it. First two times when I lowered the PH the alk dropped with it, from the lower 200s to 150. I had a suction side small air leak and was getting bubbling in my return flow that I thought would provide adequate aeration. Each time the PH rose, the alk rose along with it.

The 3rd time my PH dropped but the alk didn't really budge. I had my PH at 7.2, was aerating with return bubbling plus a bunch of normal pool activity to really stir things up. I notice after a dive or cannon ball, after the normal bubbling has stopped the surface of the pool looks like a glass of coke when you pour it and the foam goes away, carbon dioxide popping out of the pool. This is the desired result, right?

Is there a definite time frame during which the aeration must take place to get the alk to stay down?

The alk only goes down from the acid, not the aeration, right?

Pool water is crystal clear, but PH jumps back to 8ish only a few days after lowering it with acid. For some reason, the alk always goes back up with it. Am I doing something wrong?

Should I just keep dropping the PH and aerating and eventually the alk with lower and stay low?

Any help is greatly appreciated :) Oh, and I've not added any fill water since after the first time I added acid above.

When the pH starts back up, your aeration lowering effect is diminished. You have to stay right at 7.2 (lower with concrete) to see much effect.

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 :(

Can anyone help?

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.

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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.

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Nope, only using bleach. CYA is about 20ish and holding.

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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.

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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.

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This is all from info I've gleamed out of this forum, I'm still working on it myself.

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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?

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.

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Once alk is lowered and properly aerated, it shouldn't rise sharply, right?

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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.

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Originally Posted by Tredge

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

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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?

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

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Mine seems to shoot up as fast as the PH does.

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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.

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Mine too, but it's not working very well :(

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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.

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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.

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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.

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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?

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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.

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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?

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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.

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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 :)

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.

I'll be curious about your results in the morning.

The problem I was refering to about your PH climbing is an unknown....what I was trying to say is that a high TA doesnt cause the PH to rise, "somthing" else is causing them both to rise.

What that somthing else is....other than your water source...is still a mystery. Someone smarter than me will have to answer :)

I'll report back in the morning.

Looks like the rain may be re-grouping and we may get some after all. I won't hold my breath :(

From what I understood in the "lower your alk" sticky, if you don't gas of the C2O when the PH is down it can convert back and measurable alk goes back up with the PH.

I'm hoping that my previous aeration efforts were just inadequate. We'll see.

Got up early, grabbed my test kit and headed to the pool. It never did rain.

Pool had been aerating since noon yesterday.

Tested-

PH- 7.6, only dropped a bit.
Alk- 180, only dropped a bit.

I had expected a much bigger PH drop from the amount of acid I put in. I also expected the alk to be much lower.

I thought about this for awhile, and came up with a hypothesis.

In the "lower your alk" sticky thread, a poster asked if you could start aerating as soon as you add the acid. Ben responded stating it wouldn't work until the PH dropped but it probably wouldn't make a difference either way.

I'm wondering if thats correct.

If aeration increases PH while gassing off carbon dioxide to keep alk down, adding acid and immediately aerating seems counter-productive. My pool has been constantly aerated either by young swimmers or air in my return line. In looking back, the only time I got a good PH drop was when I had the air leak stopped and was getting good flow with no aeration and low swimming load.

I turned off the sump pump aeration, and added more acid, but didn't have enough to get PH as low as I need. I'll get more some time today, retest my PH and add more. I'll then try to hold the kids off from swimming tonight, retest tomorrow morning and hopefully begin aerating then.

Make any sense?

If this doesn't do it, I guess I'll be forced to live with high alkalinity and rapidly escalating PH levels :(

Interesting thoughts.
Maybe your aeration isnt enough? Or maybe you are not maintaining the PH at a low enough level for long enough....since it tends to creep up so quickly maybe its demanding more attention?

My pool is filled and I have the High TA also so I begin my aeration process tonight.

I should also have good numbers today so we can compare notes.

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Originally Posted by Tredge

Interesting thoughts.
Maybe your aeration isnt enough? Or maybe you are not maintaining the PH at a low enough level for long enough....since it tends to creep up so quickly maybe its demanding more attention?

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How long is it recommended to let the water circulate before testing PH? I gave mine a good 19 hours of circulation before testing PH. The water probably turned over 3-4 times, so it should be plenty mixed. I'm thinking the PH was dropping but being offset by the aeration so it stayed more or less stable as the end result.

I added acid this morning. I'll test ph again at noon to see what it did. This will be 5 hours later. If PH is low enough, I'll check alk. If not, I'll add more acid. I'm starting to run low on my alk reagent, and although it only costs $1.69 for another bottle with free shipping, it's a flat $6.99 "handling" fee.

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My pool is filled and I have the High TA also so I begin my aeration process tonight.

I should also have good numbers today so we can compare notes.

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Sounds great :)

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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 :(

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Hope this doesn't confuse you too much!:confused::D

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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!:confused::D

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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.

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.

After monkeying with this all weekend, I have come to the following conclusion-

Aerating WHILE adding acid to lower PH is counter-productive.

I added more acid to get to 7 (actually just a hair below), waited until I got there then fired up the sump pump aerater. The next morning the PH was still 7, so I did a bunch of cannon balls and general splashing about, then left the aerater running while we were out of town. When we got back, PH was back up to 2, so I stopped all aeration and added acid to knock it back down. Started aeration and did a bunch more manual aeration, then checked PH again before bed, it was up to 7.3. Stopped aeration, added acid and went to bed.

Continued this process through Sunday. Got the alk down to 150, this morning PH was down to 7 again so I turned on the aerater again.

In retrospect, when I was adding acid with the air leak in my return flow, it apparantly was enough to prevent the PH from dropping low enough to get carbon dioxide production, so as the PH remained stable then rose, the alk went right along with it.

Now all I need is another gallon of acid and a few more days :) I have my fingers crossed I've finally figured this out.

Tredge, what did you come up with?

Ben's sticky says you need to get PH low to induce carbon dioxide production.

Once carbon dioxide is present, I assume it's no longer measurable as part of the ALK test, and this is why we get the drop, right?

And if it's not gassed off, when PH increases due to aeration, carbon dioxide reverts back to CA, which is measurable, right?

Anyone know at what PH level carbon dioxide re-converts to CA? Waterbear?

I'm letting my TA sit high. I'm pretty happy with how the pool is balancing right now and the water looks better than ever.

If I do Aerate more out I'll probably build myself a fountain from PVC parts. Sounds like you need a Lot of aeration to make a difference in a larger pool.

Great news on your progress!

Thanks!

I think my rapidly escalating PH was related to the air bubbles in my return line.

Apparantly it's a very effective aerater, since I run my pump 24/7 :(

Now that that's fixed, I may just leave things alone and see if my PH holds steady. 14-150 in a vinyl lined pool should be fine.

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Originally Posted by Rangeball

Ben's sticky says you need to get PH low to induce carbon dioxide production.

Once carbon dioxide is present, I assume it's no longer measurable as part of the ALK test, and this is why we get the drop, right?

And if it's not gassed off, when PH increases due to aeration, carbon dioxide reverts back to CA, which is measurable, right?

Anyone know at what PH level carbon dioxide re-converts to CA? Waterbear?

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Exactly right, except that the incease in pH is due to the CO2 being gassed off...as there is less carbonic acid the pH will rise but the buffer is in equalibrium so things shift as the pH rises..It takes a bit of time and patience to lower TA. pH determines the ratio of carbonic acid to carbonates/bicarbonates in the water.....lower pH means more carbonic acid and less measurabe TA. Higher pH is the reverse. If you remove the carbonic acid by gassing off the CO2 you have lowered the TA because you have less of the total buffer system in the water. As you you lower the carbonic acid the carbonate/bicarbonate try to reach a new equalibrim so they lower. The purpose of a buffer is to stabilze pH so the pH will rise as the equalibrium is reached. The net effect is a lower TA. In most pools the TA buffer will stabililize at a pH of around 8 so the addition of acid to keep the pH in range is still necessary.

Thanks Evan. I think I finally have my head wrapped around this.

I'm 100% certain my difficulties have been from aerating WHILE trying to lower PH. Doesn't work, for me.

Now that I made progress and can live with the result, I noticed I'm down about an inch of water from evaporation (and probably my splash out from the cannon balls), and dread having to refill soon.

The guy that runs our town's water plant was in my office a few days ago. I asked him if our alkalinity always runs high (320 when I tested, with a PH of 7.2). He said yes :(

I have a vinyl lined pool. If I followed Ben's "Run a high PH" page, I'll end up over 8 with an alk in the mid 250s.

Is this a problem at all if I just let the pool do what it wants? What would I be risking?

Tested again this noon just to see where I'm at. Haven't aerated since yesterday morning.

PH was 7.2.
Alk was between 130-40. I didn't wait long enough between the drops, and the 130 drop may have been enough. I'll call it 135 :)

Since I'm this close to a good alk goal, the PH is still low and all my air leak issues seem resolved, I may go ahead and lower my ALK some more as I'm anticipating adding water again in a week or so. That way when I do hopefully I can keep alk under 200 and not worry about this much.

I'm out of acid. I guess the deciding factor will be how soon I go get some :)

We had a good rain a few days ago. Apparantly rain provides good aeration, as my PH is back up to 7.6 :)

My youngest daughter and I got in last night, and I was suprised at the amount of carbon dioxide still being released (you can see it if you wash the air bubble release after a dive or jump in). Apparantly, 7.6 is still low enough that carbon dioxide does not reconvert to carbonic acid.

I'm about 2.5" low on my water level now (we didn't get that much rain, and desperately need it :( ), so I may be forced to fight this battle again soon.

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Originally Posted by Rangeball

We had a good rain a few days ago. Apparantly rain provides good aeration, as my PH is back up to 7.6 :)

My youngest daughter and I got in last night, and I was suprised at the amount of carbon dioxide still being released (you can see it if you wash the air bubble release after a dive or jump in). Apparantly, 7.6 is still low enough that carbon dioxide does not reconvert to carbonic acid.
Just to claify...carbonic acid is carbon dioxide dissolved in the water. You alway have carbonic acid/carbonates/bicarbonates in the water...the pH just changes the proportions of each.
I'm about 2.5" low on my water level now (we didn't get that much rain, and desperately need it :( ), so I may be forced to fight this battle again soon.

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hope this is helpful.

Thanks, it was.

I was confusing CA, ie carbonic alkalinity with Carbonic Acid, ie carbon dioxide.

Since they both are CA it confused me :)

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Originally Posted by Rangeball

Thanks, it was.

I was confusing CA, ie carbonic alkalinity with Carbonic Acid, ie carbon dioxide.

Since they both are CA it confused me :)

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The proper abreviation is kH for carbonate hardness (the German form is used so it is not confused with calcium hardness)! NOt used much in the pool industry however.