CSI Pool Math

Titan7

Okay perhaps it's been too many years since college, and I was bad in math anyhow. But this whole -0.6 or .06 is confusing to follow which direction it going. So I made this chart which I assume is correct so I can easily see which direction I am heading. I always associate the number on the right of the decimal point to be negative. So hopefully this is correct, and the bold values are the outer limits of the range, the underlined numbers are the range I want to target.

1.1, 1.0, 0.9, 0.8, .07, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1, 0, -0.1, -0.2, -0.3, -0.4, -0.5, -0.6, -0.7, -0.8, -0.9,-0.10, -0.11

So if I get a value of -0.18, where is that go on the chart? Between -0.1 and -0.2? Or between -0.17 and -0.19?

Perhaps this confusion is from my recent experience sniffing too much muriatic acid, lol.

thanks

oldguy70

Silver Supporter
Okay perhaps it's been too many years since college, and I was bad in math anyhow. But this whole -0.6 or .06 is confusing to follow which direction it going. So I made this chart which I assume is correct so I can easily see which direction I am heading. I always associate the number on the right of the decimal point to be negative. So hopefully this is correct, and the bold values are the outer limits of the range, the underlined numbers are the range I want to target.

1.1, 1.0, 0.9, 0.8, .07, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1, 0, -0.1, -0.2, -0.3, -0.4, -0.5, -0.6, -0.7, -0.8, -0.9,-0.10, -0.11

Looks about right, you can play with the numbers to see what you can tweak, to stay in that 0 to -.3 range

jblizzle

TFP Expert
That is a backward number line and the number to the right of the decimal point is not "negative" as you say it is a fraction of the whole and your right 2 most numbers are wrong.

The bold is right and generally the underline range is correct.

Number lines typically have negative starting on the left and numbers increase to the right.

pooldv

TFP Expert
Platinum Supporter
Moderator Emeritus
Exactly, you want to be at -0.3 and let the CSI drift up to 0, then tweak it back down to -0.3.

Titan7

thanks, but is -0.18 fall in the 0 to -0.3?

singingpond

Well-known member
Think of it this way -- give your numbers the same number of digits after the decimal point (extend out with zeroes, which doesn't change the value of the number), and it will be easier to see. For example, compare -0.18 to -0.30. You should essentially be comparing 18 to 30, not comparing 18 to 3. So, yes, -0.18 is in between 0 to -0.3

As jblizzle pointed out, your number line is backward from how positive and negative numbers are conventionally represented. More importantly, the right two numbers are wrong. It would go:
-0.6 -0.7 -0.8 -0.9 -1.0 -1.1

Does that make sense, or is it still fuzzy?

Titan7

Got it, and thank you, that is easier.

needsajet

TFP Expert
It will help if you turn your numbers around:

(lowest number) -0.30, -0.20, -0.10, 0.00, 0.10, 0.20, 0.30 (highest number)

-0.18 is higher than -0.20 and lower than -0.10, so yes, you're on track and your result is in the target range of -0.30 to 0.00

The pattern near your result from lower to higher number is...
-0.22, -0.20, -0.18, -0.16, -0.14, etc.

Titan7

thanks, been playing with pool math, starting to make sense. I am currently at CSI = -0.47. I am trying to drop TA so I have been adding acid to a 7.2 PH and letting it drift back up. with all my other numbers remaining, once PH hits 7.4 my CSI =-0.28 which is in the 0 to -0.3 target range. Bdavis and others have told me I will drop out of range on CSI for a short time in order to bring TA numbers down.

Thanks again for everybody's help.

pooldv

TFP Expert
Platinum Supporter
Moderator Emeritus
-0.47 for a bit is fine. It will also help dissolve your white line on the tile.

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PAGirl

TFP Guide
Thank to you for this, I've been pondering the same question once or twice.

Titan7

Thank to you for this, I've been pondering the same question once or twice.

I am glad there is somebody else out there, I was starting to think i was really dumb!

With a TA of 80 my csi does the following at different PH levels. Looks like 7.4 to 7.7 is in the perfect range.

7.2 ph = -0.47
7.4 ph = -0.28
7.5 ph = -0.19
7.7 ph = 0
7.8 ph= 0.09

Tested ta again today, still at 80ppm.

Last CSI pool math question. Whats up with the Goal number? I plug in numbers to get to 0 and the goal number shows -0.49 , it never seems to change, does it work?

pooldv

TFP Expert
Platinum Supporter
Moderator Emeritus
Looking good. Welcome to TFP advanced arithmetic!

oldguy70

Silver Supporter
I am glad there is somebody else out there, I was starting to think i was really dumb!

With a TA of 80 my csi does the following at different PH levels. Looks like 7.4 to 7.7 is in the perfect range.

7.2 ph = -0.47
7.4 ph = -0.28
7.5 ph = -0.19
7.7 ph = 0
7.8 ph= 0.09

Tested ta again today, still at 80ppm.

That works but remember when something like your CH goes up or the water temp changes you have to tweak things....the 0 to -.3 is not set in concrete, you just have to be aware of what is changing and how fast it changes so you can adjust.

and yes the CSI works well.

Titan7

Thx, i have spent several hours messing with pool math and that really helps to understand the relationship between everything.

You are correct at a ta of 80 i can make everying perfect with a CH of 275, as that goes up a TA of 60-70 gives me more range.

So how many times can i safely drop ph to 7.2 which puts csi out of the range in order to drop TA?

pooldv

TFP Expert
Platinum Supporter
Moderator Emeritus
Lots of times because -0.47 is still in the safe range of -0.6 to +0.6. It is just a little better to keep it -0.3 to 0 for situations like yours, and mien, where scaling is more likely.

VinDeeLoo

Bronze Supporter
thanks, but is -0.18 fall in the 0 to -0.3?

-0.3 is the same as -0.30 so -0.18 comes before -0.30 (-0.3). 3 dimes is the same as 30 pennies. I teach my students to think of decimals as money. You just add the - sign to it on a number line.

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