Water balance struggle

[Orion6192]

So I've read all of Nitro's and ChemBear's posts and have balanced my tub before - but this time I am questioning my approach and looking for some direction.

My numbers:

TA:220

CH:320

PH:8.0

FC:5.4

CYA: 4.86 - will go to 35

Borates: 0 - will go to 50

 

I cannot get the number close to zero and I am questioning my method.  Reading Nitro's article:

1. Turn on all your jets and air features and keep them on the entire process. (i.e. Aerate)

2. Calculate how much you want to lower your TA, and how much acid you need to add to lower it.

3. Add to the tub HALF (not > 1 cup nor < 1 TBS) of the amount of the remaining acid you need to add.

4. Aerate for 30min, and check TA/pH.

5. If TA > Target and pH is > 7.8, goto step 2.

6. If TA > Target and pH is < 7.6, goto step 4 one time.

7. If TA > Target and you can't get pH > 7.8 via aeration, Target too low. Stop here.

8. If TA = Target and pH is > 7.8, Target too high. Lower Target TA and goto step 2.

 

So this I have done but I'm not sure I can get my tub to "0".  Especially with a high PH.

 

As my tub sat last night my numbers were:

TA:60

CH:320

PH:8.0

FC:5.4

CYA: 4.86 - will go to 35 eventually

Borates: 0 - will go to 50 once the rest gets dialed in.

CSI: .36

Once I hit CYA 35 and Borates 50 that takes me to .16 - again all assuming the PH of 7.8.

 

I'm targeting TA 55 which would drop me to a CSI of .1 once I hit CYA 35 and Borates 50.  Didn't have time for another cycle last night.

 

And just to be clear - PH should be measured after aerating correct?  I'm thinking more on a daily basis to check.  After aerating I can't get it below 7.8-8.0 but once it sits it may drop down to 7.6.

I'm confused - looking for someone to run the numbers and tell me what they think.

Appreciated!

Scott

 

[dlleno]

I try to simplify as much as possible, and don't go to near this amount of rigor to achieve a near-zero CSI with such precision.  The important thing to remember is that  aeration raises pH so that you can use dry acid to lower both TA and pH -- sounds like you've got that down.  As for keeping it simple I just use my spa even when TA is high, and continue to add acid for a few days until I achieve TA in the 50-ish region (I don't "adjust TA" before using the spa). 

Target pH measuring conditions are quiescent, yes.

Also keep in mind that you can go to a negative CSI without issues in an acrylic spa, and this allows some additional freedom in the pH rise department as well.   I have CH of about 100-120 and TA=40.  your CA numbers are pretty high -- can you lower that with a mixture of soft water perhaps? 

here's to negative CSI

-doug