Ideal chems targets to limit pH drift?

[Vesuvius]

I'd love to limit my pH drift by dropping TA to 60, as this approach was worked very well in my spa. However, I find it challenging to get the right mix of other levels in Pool Math that result in CSI around -0.15 (midway point of 0.0 to -0.3 target range). Here are my preferred targets:

TA 60
pH 7.6
CYA 70
CH 450
Salt 3400
BOR 40
Water Temp 80

However, at these levels, my CSI is -0.37. If I drive pH up to 8.0, I get CSI to my target at -0.14 but I feel like I'm right on the edge with pH, as my understanding is I never want it to exceed 8.0. I could push it to 7.8, but that leaves CSI at -0.24, resulting in both pH and CSI a bit closer to the edge of my acceptable ranges for both. Am I missing something? My SWG calls for 3,400 as the ideal. CSI is relatively insensitive to BOR levels. Not much room to play with CYA given recommended 60-80 range. There is some ambiguity on TFP re: acceptable CH levels (the ABCs of Pool Chem calls for 250-650 but the sticky TFPC for Beginners calls for 200-400), but even if I pushed CH up to 650, I still end up with CSI of -0.21.

Appreciate any guidance!

 

[mas985]

However, at these levels, my CSI is -0.37.

There is nothing wrong with a CSI of -0.37.

For PH, TA, CH, I focus on CSI and I regularly keep it within -0.6 and -0.3. My pool's plaster is going on 20 years old and still in fairly good condition without much etching at all. Etching really doesn't accelerate until well below -0.6.

The CSI is Reliable for Plaster-based Pools

Using the Calcium Saturation Index (also known as the LSI in the pool industry) as a guide for maintaining proper pool water balance and to protect pool plaster, including quartz and pebble finishes, has become a mainstay in our industry for good reason. Several experiments have been conducted...

www.troublefreepool.com

If I drive pH up to 8.0, I get CSI to my target at -0.14 but I feel like I'm right on the edge with pH, as my understanding is I never want it to exceed 8.0.

Only because it is really hard to measure a PH above 8.0 and because it can be an irritant to the eyes.

I could push it to 7.8, but that leaves CSI at -0.24, resulting in both pH and CSI a bit closer to the edge of my acceptable ranges for both.

You are being too restrictive about the levels. Again, there is nothing wrong with those ranges.

Am I missing something?

Don't confuse recommended ranges with absolute limits. There is a lot of margin built into the recommended ranges and operating outside of the recommended ranges is not uncommon and sometimes necessary depending on unique conditions.

There is some ambiguity on TFP re: acceptable CH levels (the ABCs of Pool Chem calls for 250-650 but the sticky TFPC for Beginners calls for 200-400), but even if I pushed CH up to 650, I still end up with CSI of -0.21.

Increasing CH would be the last thing that I would do as it is difficult to reverse. Focus on TA & PH.

However, I have operated my pool at CH levels close to 1000 ppm in the past because of very high CH fill water and drought restrictions.

 

[Vesuvius]

There is nothing wrong with a CSI of -0.37.

For PH, TA, CH, I focus on CSI and I regularly keep it within -0.6 and -0.3. My pool's plaster is going on 20 years old and still in fairly good condition without much etching at all. Etching really doesn't accelerate until well below -0.6.

The CSI is Reliable for Plaster-based Pools

Using the Calcium Saturation Index (also known as the LSI in the pool industry) as a guide for maintaining proper pool water balance and to protect pool plaster, including quartz and pebble finishes, has become a mainstay in our industry for good reason. Several experiments have been conducted...

www.troublefreepool.com

Only because it is really hard to measure a PH above 8.0 and because it can be an irritant to the eyes.


You are being too restrictive about the levels. Again, there is nothing wrong with those ranges.


Don't confuse recommended ranges with absolute limits. There is a lot of margin built into the recommended ranges and operating outside of the recommended ranges is not uncommon and sometimes necessary depending on unique conditions.


Increasing CH would be the last thing that I would do as it is difficult to reverse. Focus on TA & PH.

However, I have operated my pool at CH levels close to 1000 ppm in the past because of very high CH fill water and drought restrictions.

This is great info--thanks!