My CSI is -0.62, but my numbers are near perfect, what gives?

ajdevp

Gold Supporter
Jun 8, 2012
11
North East New Jersey
Pool Size
30000
Surface
Plaster
Chlorine
Liquid Chlorine
Hello,

Just did my numbers with Taylor K-2006 FAS-DPD chlorine kit, they are:
FC = 5.4
CC = 0
PH = 7.2
TA = 80
CH = 260
CYA 42
CSI = -0.62

Why is my CSI bordering on corrosion? I have plaster, concrete gunite pool, and my plaster is already sharp with little crystals that cut the skin.

Appreciate any inside knowledge on this, I'm very vigilant checking my water chemistry. I owe it all to Trouble Free Pool, you guys are great.

Thank you,
Adrian
 

mknauss

Mod Squad
TFP Expert
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May 3, 2014
43,975
Laughlin, NV
Pool Size
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Fiberglass
Chlorine
Salt Water Generator
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Pentair Intellichlor IC-40
ph and CH are on the low end of the acceptable range and I suspect the water temperature you have entered is pretty low?

Let the pH rise (it should on its own with a TA of 80) and the CSI will be fine. Add some calcium if you wish. Higher water temperature will raise the CSI too.
 
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CrystalRiver

Well-known member
Jun 19, 2020
648
Massachusetts
That CYA result didn't come from a Taylor kit. Taylor only gives readings in multiples of 10.

In short, your pH is at the low end, your CH isn't high, and your TA is not high. CSI is a formula that uses all of those data points, and a few more, but those three are the major contributors. With several numbers at the lower end of acceptable, the CSI is too low.

Play around with Pool Math and see how changing those numbers changes CSI. For now, I suggest raising pH, since it's the quickest and easiest to change and also very reversible. One calcium is added to the water, it only leaves when liquid water leaves the pool, so I'm slower to recommend adding that.
 

ajdevp

Gold Supporter
Jun 8, 2012
11
North East New Jersey
Pool Size
30000
Surface
Plaster
Chlorine
Liquid Chlorine
Crystal River, you're right the Taylor Kit shows CYA in multiples of ten, but when you stop seeing the black dot, the water level doesn't always land on that multiple of ten, so you have to estimate what the number is, that's what I do.

Since, we're talking about the Taylor Kit, what is your advice on the determining the CH accurately. My water turns lavender/purple before it turns blue as I add the drops. Purple isn't blue. How do you guys recommend I stop counting drops, when it's light blue, deep blue, or when it turns lavender/purple? Thank you.

Adrian
 

Texas Splash

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TFP Expert
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Jun 22, 2014
33,369
Texas, San Antonio/Marion, South-Central Area
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CircuPool RJ-45 Plus

the Taylor Kit shows CYA in multiples of ten, but when you stop seeing the black dot, the water level doesn't always land on that multiple of ten, so you have to estimate what the number is, that's what I do.
We generally recommend just rounding up or down.

My water turns lavender/purple before it turns blue as I add the drops.
Keep going until you get to the light baby blue. That's the final CH number.
 

Kellyp

Gold Supporter
Silver Supporter
Jul 5, 2018
196
Acworth ga
If I'm not sure that I'm at the end color, I add one more drop. If no change I'm done and I subtract the drop that made no change. If any change, deepening of color, brightening of color, I add another till no change detected. Always subtract the drop that made no change from your total drops counted.

This tip courtesy of mknauss, thank you sir, works every time I'm unsure.
 
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