"Adjusted TA" calculation needed for PH stabilization

[Arizonarob]

I got ya Jason, but “I” didn’t specify anything in the app. I simply entered in my pool specs, and it takes over from there.
I don’t use the pool math on the web, because I’m on my phone 99% of the time. So I use the app instead.

 

[JoyfulNoise]

I am very confused by this thread to say the least. There is absolutely nothing controversial about adjusted-TA and both TFP and Taylor agree on this matter. Adjusted TA it’s nothing more than the measured TA minus the non-carbonate alkaline species. It’s a short-hand for saying “carbonate alkalinity”. TFP’s PoolMath web page and App both do all of these calculations on the backend so the user doesn’t have to. The CSI calculation also separates out the carbonate alkalinity from cyanurate alkalinity and borate alkalinity.

Adjusted alkalinity is not what one uses to calculate pH changes as all alkaline species affect pH. The only time adjusted alkalinity is needed is when one calculates a saturation index for calcium carbonate as that is what is required by the math. So asking a user to calculate adjusted alkalinity or having PoolMath display it is not really useful.

To the OP -

I don’t understand what the confusion is here but what I am getting from your posts is that you are trying to achieve a stable (unchanging) pH. I can tell you point-blank that is not possible here in the western desert. Your pool water and fill water are loaded up with carbonate alkalinity and therefore the equilibrium pH is somewhere around 8.2. So, unless you completely strip your pool water of all carbonate alkalinity (not a good idea), your pH will always rise. The rate of rise is not a linear function of pH— pH rises faster from 7.0 to 7.5 and then slows once you get above 7.6. This is because the rate of rise in pH is dominated by the outtgassing of CO2 from pool water (your water is over-carbonated relative to atmospheric levels of CO2) and outgassing is a diffusion and mixing process which is not linear. By lowering TA, you are reducing the concentration of dissolved inorganic carbon in the water and thereby lowering the rate of outgassing. You can not practically reduce carbonate alkalinity to zero or else you will cause damage to your pool surfaces and equipment. Thus, you must live with pH rise. Adding borates can help to reduce the rate of pH rise but it then takes more acid (less frequently added) to change pH. So, even with borates, you are not using any less acid, you’re just making the pH easier to manage.

You are also using a somewhat pH neutral form of chlorination (liquid chlorine delivered by a Liquidator). There is a small amount of excess caustic in liquid chlorine (typically about 0.4 wt%) that can cause pH to rise a little bit when large amounts of chlorine are added but, by and large, liquid chlorine has minimal impact on pH and TA. Other common forms of chlorine used are acidic - triclor and dichlor. People that use stabilized chlorine see less problems with pH drift because the acidity of the chlorine source is consuming carbonate alkalinity and keeping the pH down. This is a very common problem when people switch to liquid and then are surprised that their pH keeps changing. So, since you use liquid chlorine, you also need acid on a regular basis to offset the pH rise caused by alkalinity added to your water from evaporation and fill.

 

[JoyfulNoise]

I got ya Jason, but “I” didn’t specify anything in the app. I simply entered in my pool specs, and it takes over from there.
I don’t use the pool math on the web, because I’m on my phone 99% of the time. So I use the app instead.

All of the Target values in PoolMath are user adjustable. The PoolMath app uses default values each time based on a user’s pool setup (surface type, chlorination method, etc) but the user can change the Target value in any chemical calculation.

And let’s make this point - this is not the pool store, TFP doesn’t ask users to blindly follow suggestion. Input your data and adjust target values as-needed and then think about it — if it doesn’t look right, then ask questions. This is why the Forum exists...to answer specific questions. Every pool is different and only the pool owner knows the most about what their pool needs. Pool care is not flipping hamburgers, it’s a little more complicated and requires a bit more careful thought and planning.

 

[Arizonarob]

Matt, how much MA do you go through in a week down there? I’m averaging about 4 cups of 14.5% per week to maintain a PH of 7.6-7.8.

 

[JoyfulNoise]

Matt, how much MA do you go through in a week down there? I’m averaging about 4 cups of 14.5% per week to maintain a PH of 7.6-7.8.

I add a quart of 20 Baume (31.45%) acid every 7-10 days or so. I let my pH rise to about 7.9-8.0 before adjusting it back down to 7.6. One quart of acid typically knocks the TA down by 10ppm or so. My fill water has about 110ppm TA so alkalinity creeps up with evaporation.

 

[Drd]

I know right now in my pool, my CYA is at 80 and my TA is at 70. I burn through 3 cups per day of 10% chlorine every day, and I loose an inch of water due to evaporation. My PH will hold steady for about a day or 2 at 7.5-7.6, then it will take off for 8 with no aeration going on.
Pool math app wants me to add baking soda to bump my TA up to 80, ( even though it says 70-90 is good) but I haven’t because with it at 70, I seem to at least get a day or 2 not having to add MA to the pool. When it was at 80, it climbed up daily by 2 ppm.
My CH holds steady at 270 but recently it dropped to 260 so I had to add some CH to bump it back up. I’m assuming this happened because my autofill is tapped into my water softener, and as I mentioned, I’m loosing an inch of water a day here in AZ with temps in the triple digits.

Drd, one thing I noticed is in your post you mentioned your FC was 0 and your CC was 1. It looks like you may have something organic living in the pool chewing up your FC. My CC never gets higher then 0.5, and that’s only the day after a full day of pool use with tanning lotions, sweat, etc.
Have you performed a OCLT? I think that is going to reveal something going on in your pool.

No I thought I explained, I have a feeder and I ran out of chlorine for a couple of days along with extremely hot days, I wound up with a FC of 0 and I started to get a little mustard algae but I have remedied that part. That is not my main problem, it's the TA/PH. I just don't believe we should have to babysit the pool with acid. I want to find a better solution and apparently taking the TA down is making it worse for me. Until I get a test for my salt level, I can't get a valid CSI reading right now. When I play with it and I put in just a 3000 for salt which is a guesstimate with my other test results, the CSI says -2 perfect according to the way Pool Math calculations work, which does not take into consideration the TA/CYA principles I mentioned above. I just feel I have not found the right level to keep TA at yet so ph is not bouncing up all the time and I'm going through a ton of acid which is not cheap either although I have found a better source now.

I see you have a water softener going to your outside plumbing that's what I figure I need to do was just wondering if I will add a lot of salt to the pool instead of calcium?

 

[Arizonarob]

I add a quart of 20 Baume (31.45%) acid every 7-10 days or so. I let my pH rise to about 7.9-8.0 before adjusting it back down to 7.6. One quart of acid typically knocks the TA down by 10ppm or so. My fill water has about 110ppm TA so alkalinity creeps up with evaporation.

Ok, so we’re pretty close in numbers, as your pool has about 5k gallons more then mine.
I’m going to price out the 20 Baume MA and see if it would be better then the 14.5 I’m currently using. It’s just easier to handle then the more potent stuff, but now that I have my routine down, I may switch over if the price is cheaper.
Thanks Matt.

No I thought I explained, I have a feeder and I ran out of chlorine for a couple of days along with extremely hot days, I wound up with a FC of 0 and I started to get a little mustard algae but I have remedied that part. That is not my main problem, it's the TA/PH. I just don't believe we should have to babysit the pool with acid. I want to find a better solution and apparently taking the TA down is making it worse for me. Until I get a test for my salt level, I can't get a valid CSI reading right now. When I play with it and I put in just a 3000 for salt which is a guesstimate with my other test results, the CSI says -2 perfect according to the way Pool Math calculations work, which does not take into consideration the TA/CYA principles I mentioned above. I just feel I have not found the right level to keep TA at yet so ph is not bouncing up all the time and I'm going through a ton of acid which is not cheap either although I have found a better source now.

I see you have a water softener going to your outside plumbing that's what I figure I need to do was just wondering if I will add a lot of salt to the pool instead of calcium?

Drd, I know you have a doser and ran dry, I was just looking at your CC with a raised eyebrow.

As far as softened water, the added salt is so minimal that it won’t affect your #’s that much if any.
If you’re thinking of adding a softener to your house, PM me and I have a guy that I highly recommend to everyone.

 

[JoyfulNoise]

... the CSI says -2 perfect according to the way Pool Math calculations work, which does not take into consideration the TA/CYA principles I mentioned above. I just feel I have not found the right level to keep TA at yet so ph is not bouncing up all the time and I'm going through a ton of acid which is not cheap either although I have found a better source now...

This is absolutely NOT true. TFP's CSI calculations take into account ALL necessary alkalinity calculations to come up with the CSI value. Adjusted alkalinity is not reported on either tool because it is unnecessary to report it.

Your pH bounce is not out of the norm. You reduced your TA to 60ppm and your pH increased when you added acid to lower it to 7.4. Re-read my previous post - your pool pH is always going to rise. It is a consequence of having pool water with carbonates as the buffering species. You also have a shallow pool with very warm water in it. The outgassing of CO2 is what dominates your pH rise and it will always be the major factor. Adding acid is not a one-time thing and, like every other aspect of pool water chemistry, you have to measure your pool water chemical levels daily and adjust as-needed. That's just standard pool maintenance.

 

[tim5055]

This is absolutely NOT true. TFP's CSI calculations take into account ALL necessary alkalinity calculations to come up with the CSI value. Adjusted alkalinity is not reported on either tool because it is unnecessary to report it.

Your pH bounce is not out of the norm. You reduced your TA to 60ppm and your pH increased when you added acid to lower it to 7.4. Re-read my previous post - your pool pH is always going to rise. It is a consequence of having pool water with carbonates as the buffering species. You also have a shallow pool with very warm water in it. The outgassing of CO2 is what dominates your pH rise and it will always be the major factor. Adding acid is not a one-time thing and, like every other aspect of pool water chemistry, you have to measure your pool water chemical levels daily and adjust as-needed. That's just standard pool maintenance.

This is the best answer yet.

Should you decide to raise the TA I think you are going ot find that your pH rises even faster.

 

[Dodger]

You also have a shallow pool with very warm water in it.

This.

I also have a shallow play pool and believe that contributes to pH rise more than normal deep-ended pools, since the ratio of the water surface area (in contact with air) to water volume is relatively higher. I keep my TA in the 50-60 range.

 

[Arizonarob]

This is absolutely NOT true. TFP's CSI calculations take into account ALL necessary alkalinity calculations to come up with the CSI value. Adjusted alkalinity is not reported on either tool because it is unnecessary to report it.

Your pH bounce is not out of the norm. You reduced your TA to 60ppm and your pH increased when you added acid to lower it to 7.4. Re-read my previous post - your pool pH is always going to rise. It is a consequence of having pool water with carbonates as the buffering species. You also have a shallow pool with very warm water in it. The outgassing of CO2 is what dominates your pH rise and it will always be the major factor. Adding acid is not a one-time thing and, like every other aspect of pool water chemistry, you have to measure your pool water chemical levels daily and adjust as-needed. That's just standard pool maintenance.

So, is it safe to say as the OP stated, that the TA is somewhat related to the CYA in ones pool? Meaning, if my CYA is at 80, then the pool math recommended range is 70-90, while others are keeping their TA at 50-60, which means their CYA must be in the 60 area? Does that make sense?
And if CYA does play into account, then for ME, I couldn’t imagine going any lower then 80 with the amount of sun we get here. I’d be dumping gallons of chlorine in daily to keep up with the FC loss.

 

[JoyfulNoise]

So, is it safe to say as the OP stated, that the TA is somewhat related to the CYA in ones pool? Meaning, if my CYA is at 80, then the pool math recommended range is 70-90, while others are keeping their TA at 50-60, which means their CYA must be in the 60 area? Does that make sense?
And if CYA does play into account, then for ME, I couldn’t imagine going any lower then 80 with the amount of sun we get here. I’d be dumping gallons of chlorine in daily to keep up with the FC loss.

NO. That is entirely incorrect.

You do not adjust your CYA level based on pH or TA, it is simply not a factor. The optimal TA and pH of your pool water is whatever values give you the most stable numbers with the least amount of chemical additions. If your pool water has rising pH and you lower your TA to 50ppm and it's still rising, then that's really the best you can expect (going lower than 50ppm TA can be detrimental to plaster when the pH is low). If, as is the case for some people, the pool's pH were falling, then you would raise TA (with baking soda) until you find a value that keeps your pH stable. Few people experience falling pH, most people experience rising pH.

If you want to get into the detailed chemistry of buffering capacity, read these posts -

TA--What is it really?

pH Buffer Capacity

 

[Arizonarob]

NO. That is entirely incorrect.

You do not adjust your CYA level based on pH or TA, it is simply not a factor. The optimal TA and pH of your pool water is whatever values give you the most stable numbers with the least amount of chemical additions. If your pool water has rising pH and you lower your TA to 50ppm and it's still rising, then that's really the best you can expect (going lower than 50ppm TA can be detrimental to plaster when the pH is low). If, as is the case for some people, the pool's pH were falling, then you would raise TA (with baking soda) until you find a value that keeps your pH stable. Few people experience falling pH, most people experience rising pH.

If you want to get into the detailed chemistry of buffering capacity, read these posts -

TA--What is it really?

pH Buffer Capacity

I think you read me wrong. I’m not saying to adjust your CYA, I’m asking does the CYA number dictate your TA number? Meaning the higher the CYA number, the higher ones TA range would be? (According to pool math)

 

[Arizonarob]

Matt, I read through both of those links, interesting, but I’d be lying if I said I got most of it.
But, there was one post that stood out in the TA thread that said this....

Actually I run my TA levels on the low side at around 70 ppm. Due to a large amount of my pools being communal I do have to use rather a lot of liquid Chlorine which has a very high PH 12.0+ plus the rain we get here in Spain can have a PH as high as 8.4. Quite often after a heavy downpour my PH's rise by as much as 0.6 in just one day. One of my pools with a TA of 60 rose from 7.8 to 8.4 in 24 hours after a downpour.

Is there any truth in LC having high PH levels??

 

[Leebo]

It seems like there’s a handful of discussions here. Let’s try to focus on DrD’s desire to stabilize their pH and reduce acid use.

 

[pooldv]

I think you read me wrong. I’m not saying to adjust your CYA, I’m asking does the CYA number dictate your TA number? Meaning the higher the CYA number, the higher ones TA range would be? (According to pool math)

No, CYA and TA have nothing to do with each other. CYA is set based on region, sunny and salt or not. TA level doesn't relate to CYA at all.

 

[JoyfulNoise]

I think you read me wrong. I’m not saying to adjust your CYA, I’m asking does the CYA number dictate your TA number? Meaning the higher the CYA number, the higher ones TA range would be? (According to pool math)

No. Just consider them independent. At typical pool pH values, the contribution of CYA to TA is about 1/3 of the CYA concentration. So, for example, my pool water is 90ppm CYA and a TA of 60ppm. So -

TA = Carb. Alk + Cyanurate Alk

60ppm = Carb. Alk + (1/3) * 90

Carb. Alk = 30ppm

But I do not target my TA based on my CYA. I simply ignore the CYA and adjust TA with acid as-needed. CSI calculations in PoolMath already do all the calculations to subtract cyanurate and borate alkalinity our of TA.

 

[Arizonarob]

It seems like there’s a handful of discussions here. Let’s try to focus on DrD’s desire to stabilize their pH and reduce acid use.

I’m sorry.

 

[JoyfulNoise]

Matt, I read through both of those links, interesting, but I’d be lying if I said I got most of it.
But, there was one post that stood out in the TA thread that said this....


Is there any truth in LC having high PH levels??

Large additions of liquid chlorine will drive up pH temporarily as the disproportionation of hypochlorite into hypochlorous acid uses up an H+ ion. But, chlorine reactions are mostly acidic and so the rise in pH will eventually go back down. There is some excess lye (caustic soda or sodium hydroxide) in all liquid chlorine that will also raise pH temporarily. Finally, FC levels above 10ppm will affect most pH tests causing a false high reading.

 

[Arizonarob]

No, CYA and TA have nothing to do with each other. CYA is set based on region, sunny and salt or not. TA level doesn't relate to CYA at all.

Ahhh, ok, now that makes sense.

No. Just consider them independent. At typical pool pH values, the contribution of CYA to TA is about 1/3 of the CYA concentration. So, for example, my pool water is 90ppm CYA and a TA of 60ppm. So -

TA = Carb. Alk + Cyanurate Alk

60ppm = Carb. Alk + (1/3) * 90

Carb. Alk = 30ppm

But I do not target my TA based on my CYA. I simply ignore the CYA and adjust TA with acid as-needed. CSI calculations in PoolMath already do all the calculations to subtract cyanurate and borate alkalinity our of TA.

Ok, I got it now. So the formula in PoolMath has all of that built into the end users number. Perfect.

Large additions of liquid chlorine will drive up pH temporarily as the disproportionation of hypochlorite into hypochlorous acid uses up an H+ ion. But, chlorine reactions are mostly acidic and so the rise in pH will eventually go back down. There is some excess lye (caustic soda or sodium hydroxide) in all liquid chlorine that will also raise pH temporarily. Finally, FC levels above 10ppm will affect most pH tests causing a false high reading.

So, a temp bump in PH due to addition of chlorine can be expected, but no long term level addition. Good to know. I’ll be adding MA and do my retest of the MA (to make sure my addition brings it to where it needs to be) before adding my chlorine, so as not to offset the PH reading.
Thanks Guys!!

Now back to the OP’s questions. Sorry for the hijack.