Trouble Balancing pH and TA

JLA956 · Nov 16, 2022

For some reason, I'm having a real problem balancing my pH and TA this season. I have a 400-gallon spa and use PoolMath to balance everything. I've been using the same routine for over five years now and have never had a problem - until now. I'm constantly chasing my tail trying to get the pH and TA to the proper levels. If I get my pH to 7.5 then my TA drops to around 30. I add the amount of Baking Soda that PoolMath calls for and my TA gets up to 50 or 60 where I want it to be but the pH goes off the scale on the high end. It usually takes around three ounces of Muriatic Acid to get it back down to around 7.5. Then my TA usually drops to about 20 or 30 and then the balancing act starts all over again. So far this season I've gone through about 8 ounces of acid and the same amount of baking soda.

Should I just work on getting my pH correct and not worry about the TA? Also, in the past when I got everything consistently balanced according to PoolMath, I would then add Gentle Spa and they would pretty much stay spot on until the next water change. All I would work on is keeping my FC readings in line. Until this year it's always taken about a day or two to get everything balanced but this year it's been a week and still not there yet. Any suggestions would be most appreciated.

duraleigh · Nov 16, 2022

I add the amount of Baking Soda that PoolMath calls for and my TA gets up to 50 or 60 where I want it to be but the pH goes off the scale on the high end.

Adding baking soda to your pool has little affect on your pH. Something is amiss in your testing

JohnT · Nov 16, 2022

I’d just manage pH. The primary driver behind TA is making pH management easier unless you have scaling issues.

JLA956 · Nov 16, 2022

duraleigh said:
Adding baking soda to your pool has little affect on your pH. Something is amiss in your testing

It clearly states on the PoolMath calculator that adding baking soda will increase your pH, and my experience over the last week confirms that.

JLA956 · Nov 16, 2022

JohnT said:
I’d just manage pH. The primary driver behind TA is making pH management easier unless you have scaling issues.

No scaling issues at all - I will just work on the pH and the TC. Thanks

newdude · Nov 16, 2022

For example:

duraleigh · Nov 16, 2022

It clearly states on the PoolMath calculator that adding baking soda will increase your pH

Not enough to have the affect you are describing. The pH rise is barely significant

PoolStored · Nov 16, 2022

JLA956 said:
It clearly states on the PoolMath calculator that adding baking soda will increase your pH, and my experience over the last week confirms that.

Yep, that is true. If you go to the upper left corner of the home screen in Pool Math and press on the three horizontal bars (hamburger menu), then select "EFFECTS OF ADDING." It brings you to a screen that allows you to enter/correct your pool size, select the chemical you are adding, how much and will tell you the effect of the addition on the relevant parameters.

What @duraleigh and @Newdude are saying is, that if you use this calculator, it demonstrates that the addition of baking soda will not have the effect of an extreme rise in pH you are seeing. Chemically, not possible. The likely culprit is the testing methodology, the age of your reagents, or some other factor.

How old are your reagents? What test kit are you using?

Methuselah · Nov 17, 2022

First thing I'm gong to say is this is NOT a "voice of experience" post or situation for me. That said, I'm still going to suggest something that I cannot back up with first hand knowledge...

The first rule around here is keeping things simple, not adding anything to your chemistry that you cannot account for or do not need. I see you are forcing PH and ALK changes with mercuric acid (MA) then adding baking soda to force ALK in the opposite direction. I can tell you first hand from my using MA to adjust ALK, and aeration to "fix" the PH, that I have not needed baking soda.

I suspect your perceived need to "fix" ALK with baking soda was due to either not allowing time for things to be stable before taking readings, or not giving aeration enough time to do its thing and dosing with additional MA too soon.

The fix? Well, if all I had at stake was 400 gallons of water I'd consider starting over. You don't, you also have the cost of heating and wasted chemicals. Judgement call time...

Anyway that's my $.02 as to why you had perfect success for five years and issues this one time. Another possibility I suppose is chemical interaction with something you changed this time around, like trying a new additive or using a different water source. I find that possibility less likely however, but I tend to leave no turn un-stoned.

newdude · Nov 17, 2022

@Methuselah brings up a GREAT point.

How old is the tub water ? At some point due to bather load it will get away from you no matter what. 3-6 months for most folks.

Draining very well be the path to least resistance, and you can start from scratch following the sticky atop the hot tub sub forum.

Mixing and matching methodologies is worse than sticking with a flawed one, so you have to be all in whichever way you go.

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Trouble Balancing pH and TA

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