pH, TA, and the CSI

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bpricedo

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May 20, 2012
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Here are my latest readings:

pH 8.0
FC 1.5 (water temp under 40 so not worried about this)
TA 80
CH 300
Salt 3400
CYA 70

Plugging the above numbers into the pool calculator gives me a CSI of -.27. If I lower my pH down to 7.8, the CSI goes to -.46. Down to 7.5 and its -.74.

Is there any reason my pH can't stay at 8.0? During the summer when the water temp is up I shoot for 7.5-7.8 and the CSI is higher so the lower pH is needed then. But with the colder temps the higher pH seems better. Is this correct?
 
High pH won't harm the equipment and the CSI indicates it won't be scaling nor etching the plaster, so there's no reason to fuss with it if you don't want to. The recommended pH range is what is comfortable to eyes and skin, so if no one's getting in, who cares? Just pay attention to the water temperature. If you have a warm spell CSI will change.
 
The pH of water when it gets colder is naturally higher, all else equal. This tends to keep the CSI from changing that much with temperature assuming you don't do something to compensate for the rising pH. Unless you have metals in the water for a risk of metal staining, I wouldn't worry about having the pH be somewhat on the higher side (closer to 7.8) when the water is colder and just close that way.
 
Is there any reason my pH can't stay at 8.0?
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Yes. 8.0 is outside our normal suggested range. You should keep your pH in the 7's just like you would during the swim season.
FC 1.5 (water temp under 40 so not worried about this)
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Once again, your FC is outside the normal ranges we suggest. You shouold maintain your FC at 3-5 ppm even in the winter. You will lose VERY little FC and it will prevent ANYTHING from growing if you have adequate chlorine.

Leaving a pool open in the winter means you simply maintain it like you would during the swim season......same ranges, same cleaning, etc.

If you will do that, you can ignore csi and never calculate it. The ranges we provide will automatically keep the csi at a comfortable level. Many of us here never calculate csi....ever.

FWIW, double check that water temp.....that seems VERY cold for this time of year.
 
Blaine, although I don't close my pool, I have your same dilemma about pH. In my case, with constently rising pH and the constent adding of MA it is very difficult to get TA above 80 unless I add baking soda. My fill water is high TA so it helps offset the MA additions. With high CA (around 500-550) and low TA (60 to 80) I can still keep my CSI slightly negative at pH 8.0, although I like to keep it around 7.8. I've been doing this for almost 3 years with no scaling problems.
 
Thanks everyone for the suggestions. I just don't feel comfortable getting the pH below 7.8 in this situation so I will maintain it between 7.8 and 8.0.

We had a very cold snap this last week and the water did get very cold, but maybe I did read it wrong. It certainly is below 50 at any rate.

HouTex, I think you would want your TA to be lower instead of higher. That will help keep you from having to add acid as much to keep the pH in range and also help keep your CSI slightly negative instead of positive with your high calcium. Although I have gotten my TA as low as 60 and still had to keep adding acid at the same frequency, it just seems to want to stay in the 80-90 range. I didn't notice much difference with the lower TA in my case.
 
My reasons are to keep the CSI within the range for your plaster. It seems like you are trying to say the CSI is meaningless, then why is it on the pool calculator and a range specified?

As Richard said, the pH range is for swimmer comfort and no one will be swimming through the winter, a slightly higher pH won't harm the equipment and based on the pool calculator, will be better for my plaster during the cold months.

As the temperature warms up, I adjust the pH down in the 7.5-7.8 range as recommended and my CSI stays just slightly negative. If I go down into the 7's now, my CSI gets below -.6 as explained above.

Is there a problem with this reasoning other than "you need to keep pH in the recommended range"? Seriously, I am here to learn, what problems do you think will occur if my pH is at 8 over the winter?
 

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Oh, I put a different thermometer in the water this am. The original one was reading 36F, the new one reads 43F. The Pool Pilot is telling me 42F (it only reads when the pump is running). So water is cold but not as cold as originally stated.
 
bpricedo said:
Thanks everyone for the suggestions. I just don't feel comfortable getting the pH below 7.8 in this situation so I will maintain it between 7.8 and 8.0.

We had a very cold snap this last week and the water did get very cold, but maybe I did read it wrong. It certainly is below 50 at any rate.

HouTex, I think you would want your TA to be lower instead of higher. That will help keep you from having to add acid as much to keep the pH in range and also help keep your CSI slightly negative instead of positive with your high calcium. Although I have gotten my TA as low as 60 and still had to keep adding acid at the same frequency, it just seems to want to stay in the 80-90 range. I didn't notice much difference with the lower TA in my case.
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I agree, and I also have gotten TA down to the 60 range and I still fight rising pH. My pH also seems to settle in the 8.0 range if I just let it go. Sometimes I let it stay there for a few days and so long as my TA is around 70-80 I still have a negative or low positive CSI.

If I ignored the CSI and kept all of my parameters in the usual ranges I would go crazy. I sort of tried that early on and I was replacing some water every couple of months. My main culprit is rising CH (fill water is 150 CH). It seems to have leveled off at 500-550 so I just leave it there and keep pH in the 7.6-8.0 range and with my low TA my CSI stays slightly negative. My pool and water are fine with this.
 
bpricedo said:
My reasons are to keep the CSI within the range for your plaster. It seems like you are trying to say the CSI is meaningless, then why is it on the pool calculator and a range specified?
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For most pools, keeping the parameters within the recommended ranges is easiest, but if you have a situation where you need to keep a parameter out of range, such as CH due to high CH fill water, then calculating the CSI is reasonable to figure out what you should do to TA and pH. It's on the calculator for those situations that are out of the recommended ranges or at the extremes of those ranges.
 
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