What's more important, CSI or the individual component that makes up the CSI value?

[dawei213]

So I recently had my pool redone with Wet Edge (PebbleTec competitor). I've been brushing and balancing the water the past two weeks. My numbers were good but CSI was around –0.52 but I was still working on getting it up.
PH – 7.2
TA – 80
CH – 210
CYA – 30
FC – 3
Water temp – 74
CSI – -0.52

Then this past weekend, the Wet Edge guys came out to further expose some of the pebble aggregates around the steps and bench areas. To do so, they had to pour A LOT of muriatic acid. This dropped my PH to below 6.8 I assume since the test result was very yellow and faint and TA was down to 0. So off to Costco, bought a few bags of baking soda and boxes of borax. First I raised TA back up to 80. Then I dropped in the borax. Well, I know with borax it will affect the TA but it went much higher than I expected.

Here are my current readings:
PH - 7.5
TA - 120
CH - 220
CYA - 30
FC - 3
CC 0.5
Water temp - 74 F

This gives me a CSI of -0.03.

So now I’m conflicted. My CSI is close to 0 but the TA is higher that I originally wanted and I do want to raise CH to 250 (maxed) eventually as that is what’s recommended for Wet Edge. In the Lower Total Alkalinity page (Pool School - Lower Total Alkalinity), the writer wrote that "There are two reasons to lower your total alkalinity (TA) right away, because you want to slow down the rate that the PH rises, or if high TA is contributing to a high calcium saturation index (CSI) which puts you at risk of calcium scaling. You shouldn't lower TA just to reach a target number. Make sure you actually have one of the above issues before lowering your TA.” I don’t see either issue. My question is, are these values ok for the long term? Or should I rework the chemistry to more inline on what’s recommended like this:

PH – 7.5
TA – 80
CH – 250 (maxed)
CYA – 30
Water temp – 74F
CSI - -0.18

Two more questions:

1) For the Taylor test kits, when do you stop counting the drops? So let's that the TA test, it starts out green. The instruction states to take the reading when it turns red (or in my case I see pink almost all the time). However typically it changes from green to something like grey and then an additional drop would change it to pink/red. At what point do I stop counting? At the grey or when it fully turns pink/red?

2) Is there a test kit that gives more finite ph values? The one from Taylor goes from 6.8 -> 7.2 -> 7.5 -> 7.8 -> 8.2. If a ph of 7.4 or 7.6 can make a pretty big difference in the CSI, why not have something more precise? Or all these approximate values are good enough?

 

[duraleigh]

At what point do I stop counting?

ALL drops based tests have a definitive endpoint. You continue to add drops until the last drop makes absolutely no difference (regardless of color)

Once you have determined that the last drop had no affect, you subtract that drop from the total and the remainder is your test measurement.

Is there a test kit that gives more finite pH values?

No. that pH test is the best....unless you want to spend much, much,much more and then you have a lot of calibration. In a nutshell, stay with that test....it's the best.

By the way. Don't overthink that csi. I have never tested nor paid any attention to csi. Keeping your numbers within the TFP suggested guidelines is all you need.

Lastly, your test results look really good. Nice work.

 

[pooldv]

Keeping CSI slightly negative in water with rising PH or tendency to scale is best kept -0.3 to 0. Rising PH is generally the biggest risk to scaling and high TA and waterfalls/bubblers are the biggest contributors to rising PH. Anywhere -0.3 to 0 is great.

CSI really becomes most important when you have outliers that you cannot control or keep in recommended range, like high CH (800+) in AZ. Or high TA (200-400) in some places. Where it isn't practical or possible to keep the numbers in range. Yours numbers looks like CSI should be pretty easy to manage.

 

[dawei213]

ALL drops based tests have a definitive endpoint. You continue to add drops until the last drop makes absolutely no difference (regardless of color)

Once you have determined that the last drop had no affect, you subtract that drop from the total and the remainder is your test measurement.

No. that pH test is the best....unless you want to spend much, much,much more and then you have a lot of calibration. In a nutshell, stay with that test....it's the best.

By the way. Don't overthink that csi. I have never tested nor paid any attention to csi. Keeping your numbers within the TFP suggested guidelines is all you need.

Lastly, your test results look really good. Nice work.

Thanks for the clarification on the drop test. I always thought it was when the color first changes. As for the pH test or any of the test, I guess they aren't or don't have to be precise but good enough. As long as the water chemistries are within the acceptable range, then things will be ok.

Keeping CSI slightly negative in water with rising PH or tendency to scale is best kept -0.3 to 0. Rising PH is generally the biggest risk to scaling and high TA and waterfalls/bubblers are the biggest contributors to rising PH. Anywhere -0.3 to 0 is great.

CSI really becomes most important when you have outliers that you cannot control or keep in recommended range, like high CH (800+) in AZ. Or high TA (200-400) in some places. Where it isn't practical or possible to keep the numbers in range. Yours numbers looks like CSI should be pretty easy to manage.

Ok, that makes sense. I recall you mentioning keeping it around -0.3 and 0 is good in my other thread. After redoing the test per duraleigh's instruction, my TA is more like 130. I'll definitely bring it down to at least 100 and then readjust my pH afterwards.

Thanks for both of your inputs.