Is there a certain window of time

[Rangeball]

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.

[JohnT]

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.

[Rangeball]

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

[Rangeball]

Can anyone help?

[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.

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.

[Rangeball]

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?

[Tredge]

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.

[Rangeball]

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

[Rangeball]

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.

[Tredge]

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