Impact of low TA but need it for controlling PH

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I

imureh

0
Jun 17, 2016
35
Katy
I have a two year pool where I have struggled to control the rise in PH since the start. I have tried to lower the TA now below 100ppm which has helped some but I am concerned about the impacts of low TA on the pool surface, equipment and swimmer skin/eyes. Can anybody share their expertise?

Issue 2: I have a wet edge plaster in pacific blue color but have been seeing white blotches (increasing in size with time) show up all over the pool. They have treated with dry acid and MA but no impact. I am not sure what is causing it. Could there be something leaching from the plaster that is also causing the PH control issue I mention above?

Thanks
 
Check out this article on start up of new plaster. Pool School - Start-up New Plaster At the start, all plaster pools will have significant acid demand for up to a year. Did you follow any of the methods in this article or did your builder specify how to care for the plaster initially?

The most important number for plaster is the resulting CSI for all your chemical levels combined. The CSI number is dependent on your pH, TA, CH, CYA, salt, temperature... etc. It's a total sum of your pool chemistry that lets you know if your pool has a tendency to be scaling, corrosive or neutral to your plaster. Use all your numbers and input them into the Pool Math page (like at top of page) to determine your CSI value.

Here are the TFP recommended levers for different types of pool surface and chlorination.

If you could add all the details of your pool to your forum signature, that would help: Edit Signature

Having a recommended home test kit is essential for determining your pool chemistry. How are you testing your pool?
 
I have rainbow auto inline chlorinator with Ozone. So I will post last couple of results as I have been trying to being the TA to control the PH rise. But I am not sure what issues bringing TA below 80 will cause. My fundamental issue has been rising PH and also the blotches on the plaster. Hope the below helps. I have been also taking my water to be tested by Texsun pools but they recommend looking at Adjusted Alkalinity and in most cases have me add Baking powder to raise it since its usually low due to the amount of acid needed to keep PH in line. PB states to keep PH around 7.2 which has been impossible to do and I find myself playing the game between alkalinity and PH. Thanks

Test on 6/29

FC - 4.8
PH - 7.7
TA - 90
CH - 250
CYA - 100

Test on 6/27

FC - 4.0
PH - 7.9
TA - 100
CH - 250
CYA - 100


Test on 6/19

FC - 4.0
PH - 8.0
TA - 110
CH - 250
CYA - 98
 
There is nothing wrong with low TAs in plaster pools so long as the pH and/or calcium hardness is kept a little higher to compensate.

TA has no impact on swimmer comfort.

When your numbers are entered into PoolMath, a CSI value is automatically calculated for you which is the best indicator of scale/plaster degradation potential in your pool.
 
I have the exact test results filed away so can dig them out. I do know that CH was below 200 for an extended period and PH was high above 7.8 most of the time. However there was repolish done in Nov 2014 and the water has been in balance since. Not sure why the blotches are increasing all of a sudden. My recent test results are posted above.
 
Use your numbers now. Not much you can do about past numbers.

Based on your current numbers (assuming 85 degree water, 1000 ppm salt because all pools have a little salt) your CSI is -0.06, which is good. Playing with Pool Math and changing your pH to 7.2, makes your CSI -0.5, which is getting close to a corrosive environment (where you would be leaching minerals from your plaster). Playing with Pool Math some more... if your TA is moved to 60, your CH to 350, and your pH is 7.6, then your CSI is -0.34, a pretty good spot to be. Play with your pH at these values and you'll see that maintaining your pH at 7.6 to 7.8 is ideal for CSI. Two reasons to do this. The first being the lower TA will reduce your pH rise. The second being at any TA level, pH rise is slower at higher pH levels. Maintaining 7.6-7.8 at a lower TA is much more likely to have a stable pH than a higher TA and trying to maintain 7.2-7.4 pH. The increase CH value keeps the pool from being too corrosive at your lower TA level.

The point being... play with Pool Math and see how your CSI changes at different levels. You should prefer values for TA between 60 and 80 and pH values between 7.4 and 7.8.

Aside from CSI... your CYA is getting to a point where it may be difficult to maintain sanitation. If you see the Chlorine/CYA chart in my signature, the minimum FC for 100 ppm CYA is 7 ppm. You need to maintain a minimum of 7 ppm FC at this CYA to assure that you don't get algae. Continued use of your inline chlorinator will continue to increase your CYA level. Every trichlor tablet adds CYA as it dissolves. For every 10 ppm FC added by trichlor, you add 6 ppm CYA.
 

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Unfortunately pool store testing has proven time and time to give less than reliable results.

Just because your CH is low doesn't mean that you can't get scale. An elevated pH and TA can easily cause scaling regardless of the calcium level. That's why CSI is so important in knowing the aggressiveness of your water.
 
Thanks, what would recommend I use in place of an inline chlorinator? Liquid chlorine? I have had success using Bioactive

bdavis466 said:
Unfortunately pool store testing has proven time and time to give less that reliable results.

Just because your CH is low doesn't mean that you can't get scale. An elevated pH and TA can easily cause scaling regardless of the calcium level. That's why CSI is so important in knowing the aggressiveness of your water.
Click to expand...

- - - Updated - - -

Thanks, what would you recommend I use in place of an inline chlorinator? Liquid chlorine? I have had success using Bioactive


JVTrain said:
Use your numbers now. Not much you can do about past numbers.

Based on your current numbers (assuming 85 degree water, 1000 ppm salt because all pools have a little salt) your CSI is -0.06, which is good. Playing with Pool Math and changing your pH to 7.2, makes your CSI -0.5, which is getting close to a corrosive environment (where you would be leaching minerals from your plaster). Playing with Pool Math some more... if your TA is moved to 60, your CH to 350, and your pH is 7.6, then your CSI is -0.34, a pretty good spot to be. Play with your pH at these values and you'll see that maintaining your pH at 7.6 to 7.8 is ideal for CSI. Two reasons to do this. The first being the lower TA will reduce your pH rise. The second being at any TA level, pH rise is slower at higher pH levels. Maintaining 7.6-7.8 at a lower TA is much more likely to have a stable pH than a higher TA and trying to maintain 7.2-7.4 pH. The increase CH value keeps the pool from being too corrosive at your lower TA level.

The point being... play with Pool Math and see how your CSI changes at different levels. You should prefer values for TA between 60 and 80 and pH values between 7.4 and 7.8.

Aside from CSI... your CYA is getting to a point where it may be difficult to maintain sanitation. If you see the Chlorine/CYA chart in my signature, the minimum FC for 100 ppm CYA is 7 ppm. You need to maintain a minimum of 7 ppm FC at this CYA to assure that you don't get algae. Continued use of your inline chlorinator will continue to increase your CYA level. Every trichlor tablet adds CYA as it dissolves. For every 10 ppm FC added by trichlor, you add 6 ppm CYA.
Click to expand...
 
Liquid chlorine is the most reliable and problem-free method of increasing your FC short of converting to a salt water chlorine generator system. Liquid chlorine (bleach) adds nothing to your pool other than chlorine and a small amount of salt. All other forms of solid chlorine (dichlor, trichlor, cal-hypo) add something that will build up in your pool (CYA or CH) and eventually cause problems with continued use. Except for Lithium Hypochlorite, but that is typically very expensive when compared to bleach.
 
Thanks, I will attempt to use Bioactive to get the levels down and revert to liquid chlorine and use the tabs sparingly

The issue with the blotches though is still not clear and may need another repolish. However not knowing for sure what is causing it I am reluctant to jump in and do it.

JVTrain said:
Liquid chlorine is the most reliable and problem-free method of increasing your FC short of converting to a salt water chlorine generator system. Liquid chlorine (bleach) adds nothing to your pool other than chlorine and a small amount of salt. All other forms of solid chlorine (dichlor, trichlor, cal-hypo) add something that will build up in your pool (CYA or CH) and eventually cause problems with continued use. Except for Lithium Hypochlorite, but that is typically very expensive when compared to bleach.
Click to expand...
 
Bioactive has been tried and tested by several members here on TFP with results that ranged from very limited reduction to no reduction at all. Draining some water and refilling is still the only reliable option to lower CYA. IF you have success with the product, please document it in this thread or in another thread if you like.
 
I have used Bioactive once and achieved a 40ppm decrease in CYA. So yes it did work for me.

JVTrain said:
Bioactive has been tried and tested by several members here on TFP with results that ranged from very limited reduction to no reduction at all. Draining some water and refilling is still the only reliable option to lower CYA. IF you have success with the product, please document it in this thread or in another thread if you like.
Click to expand...
 
So here is something interesting. I don't think its correct but would like to confirm. Had my water tested by Texsun pools and they advised that my TA was 95ppm and Adjusted TA is 65ppm (they always use Adjusted TA). They stated that if I do not increase the Adjusted TA to 125-150ppm it will cause algae issues and destroy the plaster. I could not understand how would Alkalinity cause algae and damage plaster when all other readings were good? Latest readings were:

FC: 1.7
PH: 7.8
TA: 95
CH: 360
CYA: 95
Borates: 60

Any views about the Alkalinity comment?

Thanks

JVTrain said:
Use your numbers now. Not much you can do about past numbers.

Based on your current numbers (assuming 85 degree water, 1000 ppm salt because all pools have a little salt) your CSI is -0.06, which is good. Playing with Pool Math and changing your pH to 7.2, makes your CSI -0.5, which is getting close to a corrosive environment (where you would be leaching minerals from your plaster). Playing with Pool Math some more... if your TA is moved to 60, your CH to 350, and your pH is 7.6, then your CSI is -0.34, a pretty good spot to be. Play with your pH at these values and you'll see that maintaining your pH at 7.6 to 7.8 is ideal for CSI. Two reasons to do this. The first being the lower TA will reduce your pH rise. The second being at any TA level, pH rise is slower at higher pH levels. Maintaining 7.6-7.8 at a lower TA is much more likely to have a stable pH than a higher TA and trying to maintain 7.2-7.4 pH. The increase CH value keeps the pool from being too corrosive at your lower TA level.

The point being... play with Pool Math and see how your CSI changes at different levels. You should prefer values for TA between 60 and 80 and pH values between 7.4 and 7.8.

Aside from CSI... your CYA is getting to a point where it may be difficult to maintain sanitation. If you see the Chlorine/CYA chart in my signature, the minimum FC for 100 ppm CYA is 7 ppm. You need to maintain a minimum of 7 ppm FC at this CYA to assure that you don't get algae. Continued use of your inline chlorinator will continue to increase your CYA level. Every trichlor tablet adds CYA as it dissolves. For every 10 ppm FC added by trichlor, you add 6 ppm CYA.
Click to expand...
 
Alkalinity and algae are unrelated.

Your TA is fine where it is if that number is accurate. The PoolMath calculator is set up to account for alkalinity corrections based on other levels. Your current numbers equate to a CSI of +0.05. You'd still be in good shape dropping your TA into the 60s.
 
imureh said:
So here is something interesting. I don't think its correct but would like to confirm. Had my water tested by Texsun pools and they advised that my TA was 95ppm and Adjusted TA is 65ppm (they always use Adjusted TA). They stated that if I do not increase the Adjusted TA to 125-150ppm it will cause algae issues and destroy the plaster. I could not understand how would Alkalinity cause algae and damage plaster when all other readings were good? Latest readings were:

FC: 1.7
PH: 7.8
TA: 95
CH: 360
CYA: 95
Borates: 60

Any views about the Alkalinity comment?

Thanks
Click to expand...

Yes. You're being pool-stored! They are trying to sell you lots of baking soda for no good reason. There is no reason to use adjusted alkalinity as a measure and, by them telling you that you need to get that up to 125ppm, that would force your total alkalinity to 170ppm. At that point, your pool would be so over saturated with aqueous carbon dioxide that your pH will rise like crazy. I doubt you'd ever get it below 7.8. With your current pool water numbers and a target value of TA at 170ppm, your CSI would be +0.52. If your pH rises to 8.0, which it almost certainly would, your CSI would go up to 0.68 and scaling would likely happen. I'm not a plaster expert, but it would not surprise me at all if all of those discolorations blooming on your pool surface is scale.

So my suggestion to you is to dump Texsun Pools, test your water yourself and follow the advice on this forum.
 

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