Keeping pH & TA at proper balance with newer plaster

[oldguy70]

This is newer plaster/pebble March 2015...I have been trying to keep my pH around 7.4 - 7.5 with TA around 95 - 100.....with that I have to add about 15 oz of acid a day and then every 3rd day or so bump up the TA with baking soda.

I had been keeping pH around 7.8, with TA around 85 - 90 but still added about 15 oz of acid daily, either way still using about the same amount daily.

Will the pH rise slow down as the plaster ages more or am I balancing the water wrong?

I understand the issue with pH reading with high chlorine and I have actually verified my numbers with the use of 2 commercial pH meters. I have also found that using the Taylor reagents, I can get reasonably accurate pH readings up to about 15 ppm FC readings. I should add, I now let the FC drift lower to about 9-10 for a very short time and check pH to again to get correct numbers.

Today's numbers:
FC 14.5
CC 0.0
pH 7.6
TA 95
CH 350
CYA 150 (I know, will handle this later)(long story here)

Thanks for any recommendations....

 

[Texas Splash]

Have you seen this page: Pool School - Start-up New Plaster. It references a 6-12 month transition period.

 

[pooldv]

I would stop raising your TA. It is fine for TA to drop to 80 at least and lower is probably OK too. As TA gets lower PH will rise slower.

 

[oldguy70]

Have you seen this page: Pool School - Start-up New Plaster. It references a 6-12 month transition period.

Yes, I did read that numerous times, I think if it had been done correctly, I may have had fewer issues. The Pool Remodel Company (3rd generation in business for over 50 years) had there own way of doing it and with the help of the pool store, I ended up with a CYA I have now.

I no longer find it a surprise that people in business are not educated/knowledgeable, don't care to learn and the worse thing is they think they are right.

I would stop raising your TA. It is fine for TA to drop to 80 at least and lower is probably OK too. As TA gets lower PH will rise slower.

I think I may do that....let the TA drop to around 80. Where should I let the pH get to before adding acid?....usually I add when it gets to around 7.7 or 7.8

 

[gilbee]

I think I may do that....let the TA drop to around 80. Where should I let the pH get to before adding acid?....usually I add when it gets to around 7.7 or 7.8

Especially with new plaster, I wouldn't let it sit at 8+ for long...by 7.8-7.9 you should be doing some figuring.

 

[JoyfulNoise]

Keeping pH & TA at proper balance with newer plaster

Why have you set a pH target so low (7.4-7.5)?

If I were in your shoes, I would lower the TA to 80ppm and just try to stay in the 7.6-7.8 pH range. Your CSI will always be less than zero. You will also add less acid.

Just for clarification, if you use a TA of 80ppm and assume a mild amount of salt in your water (500ppm) with a water temp of 88F, then your CSI would be as follows -

@pH = 7.6 -> CSI = -0.19
@pH = 8.0 -> CSI = +0.13

Those values indicate balanced water. Your CSI is 0 at a pH of roughly 7.8.


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[gilbee]

Re: Keeping pH & TA at proper balance with newer plaster

Why have you set a pH target so low (7.4-7.5)?

If I were in your shoes, I would lower the TA to 80ppm and just try to stay in the 7.6-7.8 pH range. Your CSI will always be less than zero. You will also add less acid.

Just for clarification, if you use a TA of 80ppm and assume a mild amount of salt in your water (500ppm) with a water temp of 88F, then your CSI would be as follows -

@pH = 7.6 -> CSI = -0.19
@pH = 8.0 -> CSI = +0.13

Those values indicate balanced water. Your CSI is 0 at a pH of roughly 7.8.


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I don't know about OP, but for me, if I target 7.6-7.8 with my fairly new plaster, I will be over 8 by next morning's readings.

 

[JoyfulNoise]

Re: Keeping pH & TA at proper balance with newer plaster

I don't know about OP, but for me, if I target 7.6-7.8 with my fairly new plaster, I will be over 8 by next morning's readings.

We should discuss this in a separate thread but I see from your test log (nice job on that!) that your CYA is at 50ppm. That is too low for an SWG pool. If you are running your SWG a lot to compensate for the low CYA, then the excess aeration caused by the SWG could be causing your excessive pH rise.


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[oldguy70]

Re: Keeping pH & TA at proper balance with newer plaster

I don't know about OP, but for me, if I target 7.6-7.8 with my fairly new plaster, I will be over 8 by next morning's readings.

Ya, that is why I was trying for 7.4 - 7.5, when I was up around the 7.8 - 7.9 I would be at 8+ by the next day.

I have been trying to get a handle on how much the pH rises in a day, seems to be maybe around .3 - .4

 

[JoyfulNoise]

Keeping pH & TA at proper balance with newer plaster

Ya, that is why I was trying for 7.4 - 7.5, when I was up around the 7.8 - 7.9 I would be at 8+ by the next day.

I have been trying to get a handle on how much the pH rises in a day, seems to be maybe around .3 - .4

The reason why I mentioned raising your pH target is because by going lower than 7.6 you are forcing your CSI to be negative which is counterproductive while plaster is curing. The detailed chemical explanation is covered here.

In short, you'll get off the crazy-train cycle of pH rising quicker if you keep your CSI more positive while the plaster is curing. If you target your TA and pH a little better (try for 0 or slightly positive CSI), you may be able to stretch out the time between acid additions. This is also why TFP recommends a bicarbonate plaster startup process as opposed to the hot-start process that so many in the plastering industry use. Unfortunately, you're at the mercy of the plastering company on that front.


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[gilbee]

Re: Keeping pH & TA at proper balance with newer plaster

We should discuss this in a separate thread but I see from your test log (nice job on that!) that your CYA is at 50ppm. That is too low for an SWG pool. If you are running your SWG a lot to compensate for the low CYA, then the excess aeration caused by the SWG could be causing your excessive pH rise.


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Yeah, I suppose we can, but mine wasn't intentionally 50...I didn't realize I was judging my cya inadequately high until today when I received a batch of 50ppm solution from tftestkits to see what 50 really looks like...rest assured, I'll be raising mine very soon.

 

[oldguy70]

Re: Keeping pH & TA at proper balance with newer plaster

The reason why I mentioned raising your pH target is because by going lower than 7.6 you are forcing your CSI to be negative which is counterproductive while plaster is curing. The detailed chemical explanation is covered here.

In short, you'll get off the crazy-train cycle of pH rising quicker if you keep your CSI more positive while the plaster is curing. If you target your TA and pH a little better (try for 0 or slightly positive CSI), you may be able to stretch out the time between acid additions. This is also why TFP recommends a bicarbonate plaster startup process as opposed to the hot-start process that so many in the plastering industry use. Unfortunately, you're at the mercy of the plastering company on that front.


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My problem is the high CYA, once I get that taken care of, I will able to use a lower TA and maybe a better pH number and try for a 0 or slightly positive CSI......on the subject of CSI, I was told to 'Keep your parameters within the guidelines suggested here on TFP and ignore CSI.'

With that in mind, I am probably ok with where I am now and get my CYA down, then see what I can do. I will try TA down around 80 and see if the pH will be a bit more stable.

 

[JoyfulNoise]

Re: Keeping pH & TA at proper balance with newer plaster

My problem is the high CYA, once I get that taken care of, I will able to use a lower TA and maybe a better pH number and try for a 0 or slightly positive CSI......on the subject of CSI, I was told to 'Keep your parameters within the guidelines suggested here on TFP and ignore CSI.'

With that in mind, I am probably ok with where I am now and get my CYA down, then see what I can do. I will try TA down around 80 and see if the pH will be a bit more stable.

If you have normal pool water and you follow the TFP Recommended Ranges for your pool type, then you don't have to worry about CSI since your water will be balanced by default. The recommended ranges are designed, in part, to produce a balanced CSI.

Your situation, however, is not normal. First, your CYA is way too high and requires at least a 50% water drain to bring you down to a manageable level. Second, you had a newly replastered pool surface. Therefore your ranges would be different during the curing process (higher TA and pH targets). Unfortunately your plastering company and pool store did you no favors and now you're left to clean up the mess.


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