Adding Chlorine & Acid with high CYA levels?

[oldguy70]

I have a couple of questions if anyone can help...

My latest readings:
FC 8.0
CC 0.0
pH 8.0
TA 110
CH 350
CYA 160 (I know should drain, will this late fall)
Pool Temp 90

PoolCalculator recommends to get to these numbers:
FC 14.5 add 65oz 12.5% bleach
pH 7.2 add 30oz 31.45% acid

If I understand correctly adding 65oz of chlorine with these numbers does raise the pH.

My question is should I add more acid than is recommended because of this or does the Poolcalculator take that into consideration?

 

[JVTrain]

The pH rise due to bleach addition is a temporary one and over the lifetime of the product added until the FC is consumed, is a pH neutral process. No need to compensate for pH changes due to liquid chlorine/bleach addition.

Do the acid addition first. Verify you've reached the proper pH after circulating for 30 minutes to an hour, then proceed with bleach addition after that. The pH test is not accurate above 10 FC.

Be sure you're using http://www.troublefreepool.com/calc.html not the outdated pool calculator link that is not supported by this site.

 

[chem geek]

I disagree. If you intend to keep your FC at the 8 ppm level then you can adjust the pH to where you want it to be. While the pH drops from chlorine usage/consumption, you don't intend to let your FC drop back towards 0 so the elevated pH you have now will be permanent as long as you keep your FC higher (i.e. the pH drops as FC drops, but then rises again when you add more chlorine to get the FC back up). Therefore, I would adjust your pH downward some.

 

[DaninFLA]

i think JVtrain was saying to adjust the pH first, since after he adds chlorine it will be over 10ppm and the pH test isn't accurate.

 

[oldguy70]

I disagree. If you intend to keep your FC at the 8 ppm level then you can adjust the pH to where you want it to be. While the pH drops from chlorine usage/consumption, you don't intend to let your FC drop back towards 0 so the elevated pH you have now will be permanent as long as you keep your FC higher (i.e. the pH drops as FC drops, but then rises again when you add more chlorine to get the FC back up). Therefore, I would adjust your pH downward some.

I actually intend to get the chlorine up around 14.5 ......I only let it get down to 8 or 9 to check the pH level, then kick it up to this. So if I check now and I am at 8.0 chlorine and will add 65oz of 12.5% bleach, should I then add more than the recommended of 30oz of 31.45& acid?

After adding the acid and then the chlorine I want the pH to be around 7.2

 

[chem geek]

i think JVtrain was saying to adjust the pH first, since after he adds chlorine it will be over 10ppm and the pH test isn't accurate.

In that case I misunderstood. Thanks for clarifying.

oldguy70, based on what you are saying, yes I'd have the pH be lower at your 8 ppm FC level since you intend to get it higher, but it's not a big deal since it's not a huge increase. If you started at a pH of 7.5, then with your numbers (TA, CYA) getting to 14.5 ppm FC would have the pH rise to 7.67. If you started at 7.8, however, the pH would rise to 8.1. If you started at 7.2, it would rise to 7.29 so that's probably lower than you intend (unless you wanted to lower your TA level some).

 

[oldguy70]

In that case I misunderstood. Thanks for clarifying.

oldguy70, based on what you are saying, yes I'd have the pH be lower at your 8 ppm FC level since you intend to get it higher, but it's not a big deal since it's not a huge increase. If you started at a pH of 7.5, then with your numbers (TA, CYA) getting to 14.5 ppm FC would have the pH rise to 7.67. If you started at 7.8, however, the pH would rise to 8.1. If you started at 7.2, it would rise to 7.29 so that's probably lower than you intend (unless you wanted to lower your TA level some).

I think I understand....thank You