CSI level of -0.5, what kind of harm is being done?

[platon20]

I have an SWG, current test results are: pH 7.8, FC 5.0, TC 5.5, CYA 80, Salt 3000, TA 80, CA 150, CSI -0.5

The prior season my CSI was slightly positive and I have obvious calcium scale buildup on the sides of the pool. So in order to counteract that I tried to let the CSI go negative for awhile to see if I can undo the damage of the scaling.

However, is the scaling easier to deal with than corrosion from the CSI being too low?

I'm in the process of adding calcium to bring up the CA level to around 400, which should increase CSI from -0.5 to around -0.1 or so.

Is high CSI or low CSI more damaging to the SWG? What about the pipes or the pebbletec plaster?

 

[ajw22]

I have an SWG, current test results are: pH 7.8, FC 5.0, TC 5.5, CYA 80, Salt 3000, TA 80, CA 150, CSI -0.5

What is your water temperature?

Your CSI goes down with water temperature and goes up with water temperature. Thus you get "low CSI" this time of year.

Target your pool chemistry so your CSI is slightly negative at normal summer water temperatures. Then accept low CSI in the winter.

The prior season my CSI was slightly positive and I have obvious calcium scale buildup on the sides of the pool. So in order to counteract that I tried to let the CSI go negative for awhile to see if I can undo the damage of the scaling.

That is fine.

However, is the scaling easier to deal with than corrosion from the CSI being too low?

CSI does not cause corrosion.

Low CSI creates aggressive water conditions that over long period of times can erode plaster or grout.

High CSI can lead to scaling.

I'm in the process of adding calcium to bring up the CA level to around 400, which should increase CSI from -0.5 to around -0.1 or so.

I would not increase CH past 250-300.

Is high CSI or low CSI more damaging to the SWG?

Low CSI is not damaging to a SWG.

High CSI can cause scale to accumulate on the plates and require cleaning.

What about the pipes

CSI has no effect on pipes.

or the pebbletec plaster?

Low CSI for long periods of times can etch plaster if left that way for years.

Calcium Saturation Index (CSI)

How is CSI calculated? Very simple – use our PoolMath tool. To ensure long plaster life and save money, click here to learn more.

www.troublefreepool.com

Keep your CSI between +0.6 and -0.6 and effects of CSI should not be a concern.

 

[jimim]

awesome post AJ. I'm battling the same right now and always get worried. That cold water temp wrecks havoc on the CSI.

 

[Chuckiechan]

pH 7.8, FC 5.0, TC 5.5, CYA 80, Salt 3000, TA 80, CA 150, CSI -0.5 (has SWG)
As others have said, temperature is necessary. Where are you in your wet/dry period? If you aren't having water draining out of your pool, then it's a good time to tweak your chem's. As it stands now, you are in pretty good shape.
At 70 degrees you are at .48
At 85 degrees you are at .35
You calcium may be low, wait for others to advise, but upping it to 250:
70 deg - CSI = .26
85 deg - CSI = .13