Calcium Hardness/CSI Question

[Rancho Cost-a-Lotta]

My father-in-law just completed a 100% drain and refill on a 19K gallon IG plaster pool (non-SWG). I'm helping him to get his water balanced. He tested the fill water with his new TF-100:

FC 0
CC 0
pH 7.8
TA 180
CH 180

We plan on working our way up to a CYA of 40 with Instant Liquid Conditioner, adding bleach, and adjusting pH. My question is regarding CH. Is it necessary to raise CH to the recommended 250+ range. It looks like we can achieve a negative CSI by keeping pH on the low range, which will be necessary anyways to drop the TA. Once TA is in the under 100 range, a pH of 7.6 will result in a CSI of -0.09. I hate to tell him we have to increase CH since that was a contributing factor to the pool draining. He just had his tile media blasted for calcium build-up.

Thank you,

Mike.

 

[jblizzle]

I am with you. I replaced all my water this year as well and there was no way I was going to add a lot of CH when I know it will go up 200ppm every year just due to evaporation.

Keep the CSI balanced and you should be fine.

I do not understand you statement about wanting to achieve a negative CSI to lower TA, or maybe I misunderstand your wording.

 

[Rancho Cost-a-Lotta]

I do not understand you statement about wanting to achieve a negative CSI to lower TA, or maybe I misunderstand your wording.

Thanks Jason. It makes sense in my backwards mind. I'm just saying until we get the TA down, we need to maintain pH on the lower side of the scale to achieve a negative CSI.

One more question...

When we add bleach on the fresh fill water, should we target SLAM levels or target levels according to the CYA/CL Chart?

 

[Leebo]

What is the CH level of your fill water?

 

[Rancho Cost-a-Lotta]

What is the CH level of your fill water?

CH of fresh water in the pool is 180. With the exception of what the sump pump couldn't pick up, it was a 100% refill.

 

[jblizzle]

I'm just saying until we get the TA down, we need to maintain pH on the lower side of the scale to achieve a negative CSI.

That still does not sound right.
You do not need to achieve a negative CSI to lower the TA.
To lower the TA, you need to lower the pH, which will lower the CSI, but it does not HAVE to be negative to lower the TA.
Although the CSI could get too negative at the lower pH such that you should not lower the pH as much.

 

[Rancho Cost-a-Lotta]

Thanks Jason. I just realized too the 10 ml CH test can't result in a reading of 180. I'm relying on my father-in-law's test result. I will see him Saturday and re-run the tests.

 

[Rancho Cost-a-Lotta]

One more question...

When we add bleach on the fresh fill water, should we target SLAM levels or target levels according to the CYA/CL Chart?

Any input on this question?

Mike

 

[jblizzle]

Just normal levels for a fresh fill.

 

[Rancho Cost-a-Lotta]

Thank you!