# Thread: CSI and levels for closing swimming pool

1. ## CSI and levels for closing swimming pool

Because NJ temperatures will drop accordingly and water will freeze in the pool (only a few inches at most), while the remaining water will probably stay between 34-45 * (best guess, but could be wrong), what should the levels be adjusted to:

My CSI, if I close with FC of 8 (50% of shock level based on CYA of 40), plus the addition of polyquat-60 algaecide, and where the levels are as follows:

TA 90
CH 200
CYA 40
FC 8
CC 0
PH 7.5

If the water temperature is 80 *, the CSI is -0.06. If the water temperature is 34 *, then the CSI is -0.60. If PH increases to 7.8, with water temperature at 34*, then the CSI moves up to -0.31.

Chances are that water will be warmer, probably at 40*. If this is the case, a PH of 7.8, then the CSI is -0.24. If the PH stays at 7.5, where I usually keep it at, then the CSI jumps back down to -0.54.

Does it make sense for me to increase PH to 7.8 (with aeration only) and then close the pool, Increasing the CSI and trying to get the index between the levels suggested in Pool Math? Thank you.

Please note that I am using Jesse's spreadsheet, but have confirmed the CSI in Pool Math.

2. ## Re: CSI and levels for closing swimming pool

I don't know if I'd be that worried about it. Your pH is NOT going to stay below 7.6 for very long and there's plenty of warm-ish East coast weather between now and winter. But, I see no harm in raising it up to 7.6 before you button it all up for the winter.

3. ## Re: CSI and levels for closing swimming pool

Originally Posted by JoyfulNoise
I don't know if I'd be that worried about it. Your pH is NOT going to stay below 7.6 for very long and there's plenty of warm-ish East coast weather between now and winter. But, I see no harm in raising it up to 7.6 before you button it all up for the winter. Sent from my iPhone using Tapatalk
Does the PH drift up over the winter months? (while sitting idle and hibernating). Or could this be the combination of algaecide and some chlorine sitting there for 7 months?

Last year, I closed at 7.6 and started at 7.2. It appears that PH drifted lower. I was thinking of raising it, if PH drifts down over the winter, so it does not get too low.

4. ## Re: CSI and levels for closing swimming pool

Originally Posted by Catanzaro
Does the PH drift up over the winter months? (while sitting idle and hibernating). Or could this be the combination of algaecide and some chlorine sitting there for 7 months?

Last year, I closed at 7.6 and started at 7.2. It appears that PH drifted lower. I was thinking of raising it, if PH drifts down over the winter, so it does not get too low.
Oh right, Jersey vinyl pool....I would then go with your past experience that it drops. And that is better because, honestly, vinyl pools are not that sensitive to CSI. Most vinyl owners don't really care about CSI unless it gets really positive. What's damaging to vinyl is a combination of low pH (embrittlement) and high FC (bleaching/oxidation). If your pH ends the season a little high (7.6) and drops to 7.2 at opening, you'll be absolutely fine.

5. ## Re: CSI and levels for closing swimming pool

If there is no carbon dioxide outgassing or anything else going on in the pool, then colder temperature has the pH rise while warmer temperature has the pH drop. So this tends to counteract the temperature change of CSI. So you can just see if that happens and only adjust the pH higher if you find that it doesn't rise for some reason, but I suspect it will on its own. Basically, the equilibrium between water and hydrogen ions (that determine pH) is temperature-dependent.

6. ## Re: CSI and levels for closing swimming pool

Originally Posted by chem geek
If there is no carbon dioxide outgassing or anything else going on in the pool, then colder temperature has the pH rise while warmer temperature has the pH drop. So this tends to counteract the temperature change of CSI. So you can just see if that happens and only adjust the pH higher if you find that it doesn't rise for some reason, but I suspect it will on its own. Basically, the equilibrium between water and hydrogen ions (that determine pH) is temperature-dependent.
Chem-Geek:

Please remember that in about 7-10 days, the pool will be closed and covered with a regular pool cover. Unfortunately, there will be too many leaves, nuts, etc. in the pool to maintain it properly.

I can easily check PH every few weeks to determine if it has risen or dropped. Should I be overly concerned about CSI when the pool is closed, especially given that this is a liner pool? Raising PH, prior to closing, will change the CSI in a favorable direction. Also, the water will just be sitting there and not being circulated. I do not want the PH to a range that could be corrosive in nature. Thank you.

7. ## Re: CSI and levels for closing swimming pool

Originally Posted by Catanzaro
I can easily check PH every few weeks to determine if it has risen or dropped. Should I be overly concerned about CSI when the pool is closed, especially given that this is a liner pool? Raising PH, prior to closing, will change the CSI in a favorable direction. Also, the water will just be sitting there and not being circulated. I do not want the PH to a range that could be corrosive in nature. Thank you.
With a vinyl pool there is no need to worry about CSI unless your numbers get WAY out of line....in which the numbers you're mentioning is just fine. In the several years I've closed our pool for the winter I've never once worried about the pH during the winter and haven't had a problem at all. Close it up and dream of opening next year.

8. ## Re: CSI and levels for closing swimming pool

Yeah, negative CSI is not a problem for vinyl. That's only for protecting the calcium carbonate in plaster and grout. Sorry I missed that. Metal corrosion isn't so dependent on CSI but rather on low pH that is the main problem.

9. ## Re: CSI and levels for closing swimming pool

Thank you everyone.

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