CSI questions & thoughts

[bware]

Having joined TFP this past spring, I have had a sparkly clean and trouble free pool all summer and have thoroughly enjoyed the process of regular testing and listening to all the ooos and aahhs of a clean, good looking pool.

PH 7.2
FC 6
CC 0
CH 425 (fill 75)
TA 60 (fill 275)
CYA 80
Temp 88-90

How concerned should I be when bringing PH from 7.8 to 7.2 and TA from 80 to 60 adding MA according to Pool Math and CSI reads -0.66 and corrosion likely?

In the summer I add MA every week to 10 days and usually it is in the above range in order to keep my TA down. I was hoping for a leveling off on PH by now, but that may not happen with SWG, falls and plaster. I was surprised to see my fill water TA is 275, but have read since many others have higher.

Since this CSI level only lasts for a few days till levels start drifting up, I'm wondering if it's a big deal.

I know it spent a lot of time at the other end before TFP, since there was lots of scaling back then and much more frequent cell cleaning.

Thoughts?

 

[BuckeyeChris]

I get -0.42 when using your current readings above. If pH and TA will only drift up from there, you should be fine.

Why not just let the TA sit at 70? that will add .1 to your index. and as you keep adding fill water, getting to 550 CH will add another .1. Targeting 7.4 pH will also add .15.

with rising pH due to higher TA, the pH will go from 7.2 to 7.5 much faster than from 7.5 to 7.8, so you probably don't need to aim that low. Since your CURRENT TA is 60, you aren't actively trying to lower the TA of the whole pool. Just fighting the fill water. Aiming for 7.4 would keep it from getting to high, I'd think, but perhaps in your experience it will raise much faster?

 

[bware]

Strange. I ran my numbers again in Poolmath and came up with -0.64 so don't know why the difference. When did my weekly testing yesterday, I had pH 7.8 and TA 80 with all other numbers same as current so I added the MA and that brought them to present reading. I do target TA at 70 and pH at 7.5, but I try to head off the dreaded over 8 number and dose it accordingly...like you say, I probably will fight it with the high TA from fill. Maybe just catching it at 7.8 and bringing it to 7.5 is the answer but sticky on lowering TA says bring pH to 7.2 so that's what I've done so far. Thanks for your thoughts on this.

 

[BuckeyeChris]

probably splitting hairs here, a bit more every 10 days or just a bit less every 7 days.

 

[Agent99]

Without your salt concentration, we cannot calculate the CSI accurately. I have a feeling my namesake above left it at 0.

I get -0.62 using 3200 ppm NaCl. Increasing the temp reduces the CSI, BTW. I used 88 F.

pH has the largest impact on CSI so going from 7.2 to 7.5 brings you to -0.25 and to 7.8 gets you +0.02. Hitting 8 is +0.21...8.2 +0.4.

I agree with BuckeyeChris there, just leave things be and let the pH rise and knock 'er back down with MA.

TA is the least important of parameter to worry about and deal with. Who knows, maybe if you let your TA continue to drop, you might find the pH to level off...or not. Besides, your fill water will add some TA as well. Steady as she goes with MA!

 

[bware]

Salt is 3300 and temp is 89...should have included in first post. I agree with you both, I think I will just dose the MA to keep it at 7.5 which should keep TA around 70 and no more than 80 and let it ride.
Thanks again for the input!