Bleach raise PH?

[mkohr]

1st season using the TFP method and its awesome!
However i noticed that it appears as if the bleach raises the PH is that typical?
Every few days i need to add a little acid.

 

[JoyfulNoise]

Yes. Most bleach contains excess lye (sodium hydroxide) from the manufacturing process. It also contains some salt. Regular additions of muriatic acid are normal.

What are your latest test numbers?


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[mkohr]

Fc 6.5
cc .5
Alk 100
Cya 40
PH 8.2 ish


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[JoyfulNoise]

Your pH is quite high as 8.2 is the max. Your TA is fine and should only be contributing a small amount to your pH rise.

How much acid do your normally add and what pH are you targeting? Also, how much bleach is your Stenner pump supplying each day?

What's your fill water like?


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[mkohr]

I have the pump set to add about 3/4 gallon of 12.5% each day it seems to keep my FC in the 4-8 range. Almost every time I check CC it's 0 to.5 as high as 1.0 to 1.5 after Harvey rain. The next day returns to 0 to .5
I figure 7.5 is a good PH target ????
Pool math told me to add 42 oz of acid.



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[JoyfulNoise]

I have the pump set to add about 3/4 gallon of 12.5% each day it seems to keep my FC in the 4-8 range. Almost every time I check CC it's 0 to.5 as high as 1.0 to 1.5 after Harvey rain. The next day returns to 0 to .5
I figure 7.5 is a good PH target ????
Pool math told me to add 42 oz of acid.



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So in your pool, 96oz is 3.7ppm FC per day. That seems a bit high to me in terms of chlorine usage but not unusual if your pool gets lots of sun. Your CYA is 40ppm which is right in the middle of the suggested range. If your pool does get a lot of sun exposure, you could try bumping the CYA up to 50ppm and then see if you lose less FC per day.

You might also try raising your FC up to 10ppm manually (shut off the Stenner) and perform an OCLT to see if you're losing less than 1ppm overnight.

A pH of 7.5 is perfect.

If none of the above helps, then you could try dropping your TA down to 60 or 70ppm to see if that helps maintain a more stable pH. After that, if the pH rise is still an issue, 50ppm borates with a lower TA target might help. But that's only after exhausting all the simple solutions.


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[mkohr]

The pool is in 100% all sun , no shade expect for very early and very late in the day


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[JoyfulNoise]

Then definitely consider a bump in your CYA. I bet the sun exposure is adding to your chlorine demand. Many of the TX folks who do chlorine manually or with a Stenner report staying on the higher end of CYA during the hot sunny months. I'd bet that's true even for you Hoosiers

Oops, my bad. Yore not in Indiana but PA. Apologies

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[mkohr]

I did a OCLT as per your recommendation ...
Less then 1.0 FC loss
And .5 CC
I also waited he 12 hours and tested again in the evening. It was an all sun , blue sky. 80+ degree day.
My FC loss was 5 and Cc was between .5 and 1.0


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[chem geek]

Your CYA level is too low for the amount of sun in your pool.

As for pH rise, the TA of 100 ppm is likely contributing to that. Most chlorinating liquid or bleach does not have enough excess lye in it to be a major contributor to rising pH. Most rising pH in residential pools comes from carbon dioxide outgassing from the water and that happens faster at higher TA and lower pH.

With regular acid additions to lower the pH you should find your TA slowly dropping over time in which case the rate of pH rise should slow. If you want to accelerate this process you can follow the Pool School article on how to Lower Total Alkalinity.

 

[mkohr]

What would you recommend my CYA be? In the beginning of the season i was advised to drain about 10,000 gallons to get my CYA down from the 90+ range, maybe i went to far.
Also what is the downside at leaving it where it is at, other than the cost of adding almost 1 gallon of bleach each day?

 

[tim5055]

Other than the extra chlorine you are using, no real downside. Mine is also in full sun all day and 50ish is good for me.

 

[mkohr]

How much granular shock or tabs would bring me upto 50CYa?


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