CSI

[MyAZPool]

Now that the water temp has cooled quite a bit over the last week, pool math now shows my CSI below acceptable level (Potential to become corrosive to plaster). Pool math now shows a target CSI of -0.43. My current CSI is: -0.33

Since getting on board with Pool School, I've been doing a good job of keeping all chem levels in range and very close to my targets. But I'm still a little shaky about CSI, so I could use a little advice. Which is better to get back to the recommended target CSI?

Add about 8 oz of stabilizer (granular) to bring my CYA up to 75?
or
Add a cup of acid (28.3) to lower pH to 7.4?
or
Add about 24 oz or baking soda to get TA to 75?

Here are my numbers:
TEMP: 72
pH: 7.5
FC: 6
CC: 0.2
TA: 70
CH: 575
CYA: 72
Borates: 50
Salt: 4000
CSI: -0.33

Thanks in advance!
r.

 

[JamesW]

I would just allow the pH to rise to 7.8.

Brush the pool at least once a week.

 

[jblizzle]

There is no "target CSI" that you should be trying to achieve. You just want to keep it relatively neutral. With a SWG, perhaps keep it slightly negative (between -0.3 and -0.1)

The CSI is just a calculation based on all the parameter values you have entered into then Now and Target columns.
With a CSI of -0.33 now, I would not be looking to drive it more negative.

 

[MyAZPool]

I would just allow the pH to rise to 7.8.

Brush the pool at least once a week.

Thanks James. I do brush once a week in winter and more in the summer. So no problem there.
When I plug 7.8 into pool math it actually raises CSI. According to pool math, it says I need to lower CSI from -0.33 to -0.43, not raise it. If I let pH rise to 7.8, I'll be at -0.11?

 

[jblizzle]

See my above post.

 

[MyAZPool]

There is no "target CSI" that you should be trying to achieve. You just want to keep it relatively neutral. With a SWG, perhaps keep it slightly negative (between -0.3 and -0.1)

The CSI is just a calculation based on all the parameter values you have entered into then Now and Target columns.
With a CSI of -0.33 now, I would not be looking to drive it more negative.

Oh, okay, so disregard the "target" number that pool math throws in there and just use a target range of -0.3 to -0.1. Got it.
Thanks much Jason!

Is adjusting pH the most effective way of adjusting the CSI?
r.

 

[jblizzle]

Yes, pH generally has the largest impact on CSI.

Well, don't ignore the Target CSI. That is the CSI that would result from all the values you entered in as your Targets. So if you made all those adjustments, it is the CSI you would get.

 

[MyAZPool]

Yes, pH generally has the largest impact on CSI.

Well, don't ignore the Target CSI. That is the CSI that would result from all the values you entered in as your Targets. So if you made all those adjustments, it is the CSI you would get.

Okay, I get it now... Thank you Sir!!

 

[triptyx]

Be ready to chase that CSI all winter - as the water cools, the CSI will get lower and lower. Keep your pH higher to compensate - and let your TA rise (if Phoenix water is anything like Tucson's, your TA should go up over time if you're not aggressively lowering pH to keep it in check). I keep a close eye on my CSI in the winter because the colder water definitely can cause corrosive conditions if you're keeping your pH lower. No worries, don't sweat it, just test a couple of times a month and keep an eye on things.

 

[jblizzle]

I found the opposite problem last year in that the CSI got much too high over the winter which cause some scaling to start in the water. My CH was not even above 300ppm I don't think. So, the pH must have climbed very high.

Bottom line, don't just ignore the pool over the winter

 

[triptyx]

I found the opposite problem last year in that the CSI got much too high over the winter which cause some scaling to start in the water. My CH was not even above 300ppm I don't think. So, the pH must have climbed very high.

Bottom line, don't just ignore the pool over the winter

Good advice.

 

[MyAZPool]

Be ready to chase that CSI all winter - as the water cools, the CSI will get lower and lower. Keep your pH higher to compensate - and let your TA rise (if Phoenix water is anything like Tucson's, your TA should go up over time if you're not aggressively lowering pH to keep it in check). I keep a close eye on my CSI in the winter because the colder water definitely can cause corrosive conditions if you're keeping your pH lower. No worries, don't sweat it, just test a couple of times a month and keep an eye on things.

I found the opposite problem last year in that the CSI got much too high over the winter which cause some scaling to start in the water. My CH was not even above 300ppm I don't think. So, the pH must have climbed very high.

Bottom line, don't just ignore the pool over the winter

Thanks all. I'll just keep an eye on it over the winter. I'll let my pH drift up a bit from 7.5 to maybe 7.7 and see if that keeps my CSI where it needs to be (-0.3 to -0.1). Thanks again!

 

[Bvacchiano]

Am I missing something? My CSI calculator from TFP says for plaster keep it at greater than -.6. So a value of -.5 should be fine right?

 

[mknauss]

It is OK, but it is best to leave a cushion by keeping it above -0.3.

 

[MyAZPool]

Am I missing something? My CSI calculator from TFP says for plaster keep it at greater than -.6. So a value of -.5 should be fine right?

I noticed that you have an IC-40. Many of the folks here have stated that keeping CSI slightly on the negative side (-0.3 to -0.1) is more acceptable if you have a salt pool.

Since I have started this thread, I have read quite a bit about CSI here on TFP. My take-away is that maintaining pH, CH and TA all within the suggested ranges will most likely keep CSI in range in most instances. And to not get too "wrapped-around-the-axle" about minor excursions but just keep an eye on it and not chase it.

I have also took note that letting pH go up slightly more in the winter than where you keep it at in the summer will help. I try to keep pH at 7.5 in the summer and so this winter, I will try to maintain pH in the 7.7 range and see if that has a more positive effect of keeping my CSI in the -0.3 to -0.1 range.

I'm glad I started this thread, as I got some good and simple advice about CSI (something I did not really care about in the past) and how pool math calculates the target CSI. Thanks to all who contributed.

 

[Mickey Moose]

Here is my CSI for the last few months. I can explain the spikes and dips if desired though, for now at least, I suggest they be ignored. The chart shows CSI starting to drift down which is a result of water temperature dropping. Generally speaking I don't chase CSI as it will be kept in check by maintaining all other measures. During Winter I will make a few adjustments as necessary to keep it in check. The next/first adjustment will be when the water drops about another 20F. That adjustment might get me through until temp start to warm.