PH & Alkalinity

[missourian]

Hello All,

I have been playing cat and mouse game for almost 6 weeks, my alkalinity dropped to 60, so I keep adding baking soda to bring alkalinity to 90, this process raises the PH to above 8, by the time I reduce the PH to 7.4 with muriatic acid alkalinity drops back. I really appreciate an recommendation on how to tackle this problem.

 

[woodyp]

According to Pool Math, you should only need 85 ounces of baking soda to raise your TA by 30 and this should only raise your PH by .06 which is negligible. How much are you adding and how are you testing?
Sounds like your PH is borderline high before adding the baking soda.

Conversely, it should only take 20 ounces of muriatic acid to lower your PH from 8 to 7.4, which lowers your TA by 6. Close enough for hand grenades and horseshoes on TA level.

 

[JasonLion]

by the time I reduce the PH to 7.4 with muriatic acid

I'm wondering about your word choice. Lowering PH should only take half an hour to an hour.

It would be a big help if you could post a full set of test results. Also, do you have a waterfall, spa, fountain, negative edge, etc that is getting used during this period? And finally, do you have a SWG?

 

[woodyp]

"Also, do you have a waterfall, spa, fountain, negative edge, etc that is getting used during this period? And finally, do you have a SWG? "--Jason

ALL of those will raise PH btw.

 

[missourian]

Thanks, I added 5 lbs of baking soda last time and I was adding muriatic acid two to three times a week to keep the Ph around 7.5, this morning when I tested the alkalinity it went back to 60, I use TF 100 for all my testing.

 

[JasonLion]

Try not adding nearly as much baking soda at one time as you have been doing, and also don't lower the PH quite as much.

PH tends to drift up. The higher your TA, and the lower your PH, the faster PH will go up. Adding acid lowers both PH and TA, though it lowers PH way more quickly than TA. So if you are adding acid regularly, the TA will go down.

In many cases it is possible to get the PH to settle around 7.7 when TA is around 60. If not, adding borates often help stabilize things, and also allows you to lower TA a little further, further slowing PH increases.

 

[missourian]

Re: PH & Alkalinity

I'm wondering about your word choice. Lowering PH should only take half an hour to an hour.

It would be a big help if you could post a full set of test results. Also, do you have a waterfall, spa, fountain, negative edge, etc that is getting used during this period? And finally, do you have a SWG?

"Also, do you have a waterfall, spa, fountain, negative edge, etc that is getting used during this period? And finally, do you have a SWG? "--Jason

ALL of those will raise PH btw.

Yes, I have waterfall and spa and I keep it running for 12 hours daily, No I don't have SWG, My complete test results;

PH 7.5
FC 4.5
CC 0.5
Alk 60
Cal Hard 300
CYA 50

I have been following BBB since last august (I am not using Borax), Apart from daily bleach routine, weekly twice or thrice I add muriatic acid to bring the PH down as it always drift up to close to 8.

- - - Updated - - -

Try not adding nearly as much baking soda at one time as you have been doing, and also don't lower the PH quite as much.

PH tends to drift up. The higher your TA, and the lower your PH, the faster PH will go up. Adding acid lowers both PH and TA, though it lowers PH way more quickly than TA. So if you are adding acid regularly, the TA will go down.

In many cases it is possible to get the PH to settle around 7.7 when TA is around 60. If not, adding borates often help stabilize things, and also allows you to lower TA a little further, further slowing PH increases.

Thanks Jason, I will follow this recommendation, I originally planned to add Borax into the mix by this summer may be I shouldn't wait.

 

[woodyp]

You should add those items into your profile/signature line.

 

[Richard320]

Maybe 60 TA is the sweet spot for your pool? If you don't raise it, how long can you go before pH rises to where you need to add acid again? Remember, those target values are guidelines; they aren't absolute; least of all the TA level. Without knowing the water temperature, it's impossible to say what the CSI is for certain, but at a reasonable guess of 65F, you're still essentially neutral, slightly negative in fact, which is okay with your vinyl liner since it won't etch like a plaster surface.

Try not adding any baking soda and keep an eye on pH. Maybe your pool will just sit there all year with a steady pH if you just leave TA where it is. That's my suggestion.

 

[Patrick_B]

Again I agree. Don't focus on TA, but pH instead. It is vastly more important, almost always.