pH over 8 but CSI almost 0...OK?

gilbee

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Mar 31, 2015
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Harvey, LA
Just want to sanity check...with my numbers my CSI is currently at -.08, even with a pH of 8.2....before I go running to drop it back to 7.8 (I'll prob do it later today or tomorrow morning), is it ok to run that high as long as the CSI is happily balanced?
 

jblizzle

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Generally that is correct.

The problem is there is no way to know just how high the pH really is since you are at the top of the testing range.
 

JoyfulNoise

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May 23, 2015
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If you post a full set of test results, the experts here can better help you target your water values.

If your pH is 8.2 and your CSI is still negative, then either your CH or TA or both are really low. That might be ok if your pool is vinyl but more details would help.


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gilbee

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Mar 31, 2015
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Harvey, LA
JoyfulNoise, as you know, my test results are always in my sig. I've been kinda lazy this week, and will be grabbing full numbers tomorrow, but I expect TA to be around 70 and CH to be around 325-350
 

JoyfulNoise

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JoyfulNoise, as you know, my test results are always in my sig. I've been kinda lazy this week, and will be grabbing full numbers tomorrow, but I expect TA to be around 70 and CH to be around 325-350
Wow. My bad. I totally missed that you were the OP. I need more coffee ;)


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gilbee

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Mar 31, 2015
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Harvey, LA
Yup, and added borates a week or two ago...I'm able to ride about 3-4 days between acid additions now, which is a vast improvement over the previous arrangement. I feel confident with the swg and the borates that if I had to leave the pool for a few days for work that it won't be affected by my neglect by absence.
 

JoyfulNoise

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May 23, 2015
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Are you able to get the TA any lower or is the fill water too high? I once tried dropping my TA to 50ppm (when evap losses are lower in the winter) and my pH was rock solid stable for long stretches. I can cut down the water feature use in the winter quite a bit and that really helps as well.


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duraleigh

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This thread brings up a couple of points. Test results shouldn't be in a sig because they are a snapshot in time. Sig stuff is more permanent.

Secondly, CSI drives me nuts. It may or may not be OK to run your pool like that but rather than dwell on CSI (which many love to do) simply keep your pool within the parameters suggested at TFP and you have no worries.
 

Divin Dave

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Oct 2, 2013
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Longview, Texas
Either im wrong or you need to recheck your CSI in pool math, or your test results. Using the following numbers, Pool math says your CSI is +0.48
17.4K gallons water
FC 7.5
Ph 8.2
TA 80
CH 325
CYA 40
Salt level I did not find on your spread sheet - so I used 0
Borate I did not find on your spreadsheet - so I used 0
Temp - I guessed at 87.

Your spreadsheet is diffiucult for people trying to help you to use. You dont list ALL of the water parameters every day. I had to scroll up and down a few times to find the most recent values for TA and CH. If you will note the TA, CH, and Salt and Borates each day at what you consider them to be if didnt test them. That would be more user friendly to us.

So, I would suggest review the values you used in Pool Math to come up with a -.08 wiith those numbers
 

JamesW

TFP Expert
Mar 2, 2011
20,696
I can get -0.08 with the following:
pH = 8.2
TA = 70
CH = 325
CYA = 70
Salt = 3,200
Borate = 50
Temp = 84

The OP does have a SWG and has added borates.

In any case, I would keep the pH below 8.0.
 

gilbee

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Mar 31, 2015
300
Harvey, LA
This thread brings up a couple of points. Test results shouldn't be in a sig because they are a snapshot in time. Sig stuff is more permanent.
Duraleigh,

The sig has a link to a spreadsheet that I update (mostly daily) that has my readings. I try to take a full set of readings once a week, and otherwise just post FC,CC,TC, and pH. No actual readings are in the sig itself, you simply click the link in there and it shows you a historical of all of my tests.


Either im wrong or you need to recheck your CSI in pool math, or your test results. Using the following numbers, Pool math says your CSI is +0.48
17.4K gallons water
FC 7.5
Ph 8.2
TA 80
CH 325
CYA 40
Salt level I did not find on your spread sheet - so I used 0
Borate I did not find on your spreadsheet - so I used 0
Temp - I guessed at 87.

Your spreadsheet is diffiucult for people trying to help you to use. You dont list ALL of the water parameters every day. I had to scroll up and down a few times to find the most recent values for TA and CH. If you will note the TA, CH, and Salt and Borates each day at what you consider them to be if didnt test them. That would be more user friendly to us.

So, I would suggest review the values you used in Pool Math to come up with a -.08 wiith those numbers
Divin Dave,
The point here wasn't to bring anyones attention to my actual readings...I wanted to talk about this based on the logic and theory of it. Either it works based on certain parameters, or it doesn't. My numbers (or missing ones in the past few days) only clouds the question I wanted an answer to, which was "Is it ok to have a pH over 8 if the CSI shows balanced. JamesW has more or less correctly inferred my numbers (I think I have 3300ppm salt, a negligible difference), but the point of my question wasn't to ask about my specific numbers, but to ask generally about the practice. If I were posting this in the getting started board with a "what should I do" at the end of it, my numbers are definitely a must...for this question, I was more looking for theory and the science for it/against it and my specific numbers while not irrelevant, shouldn't be required to discuss this piece of minutiae.

Duraleigh,
If the CSI isn't a good measure and some of us seem hung up on it (and lots of discussion revolves around it), why do we even use it? If the formula is supposed to yield whether water is balanced, and the formula shows balanced water, why is it to be ignored when it potentially is cross to the general TFP chemistry? If we are to keep a CSI in the -.3 to .3 range, using the numbers JamesW put out there, I've got 7.7-7.9 that I can ride on to be within CSI but also follow TFP guidelines, and based on TFP guidelines for SWG:

"Adjust your pH to 7.5-7.6 and not any lower. Monitor your pH and when it climbs to 7.8 add acid to lower it back to 7.5-7.6 (This is also IMPORTANT!)"

I would NEVER be targeting a balanced CSI. In addition, some forum members (JoyfulNoise is the one I notice the most, and backs up what is said with great info and data) cites a reasonable guidance to maintain a slightly positive if not completely balanced CSI on newer plaster pools...something's gotta give somewhere, and is that something the TFP pH guidance, or the CSI? I'm not saying I have it in my head of which one, I'm just trying to sort out which should give deference to the other.
 

JoyfulNoise

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I would NEVER be targeting a balanced CSI. In addition, some forum members (JoyfulNoise is the one I notice the most, and backs up what is said with great info and data) cites a reasonable guidance to maintain a slightly positive if not completely balanced CSI on newer plaster pools...something's gotta give somewhere, and is that something the TFP pH guidance, or the CSI? I'm not saying I have it in my head of which one, I'm just trying to sort out which should give deference to the other.
With respect to the TFP Recommended ranges and CSI, I think this is a false choice. The Recommended Ranges are specifically designed so that the vast majority of pool owners can follow them, have balanced water and not have to think about CSI. That's whole purpose of TFP - make it easy so that folks don't have to fiddle around with complicated calculations or base dosing decisions on a parameter like CSI. For vinyl pools, the CSI can all but be ignored as long as the pool owner is following the recommended ranges since negative CSI is really not an issue and a positive CSI only causes scaling problems for vinyl when the water parameters are far outside their recommended ranges.

I think your pool is a special case because you did three very significant things to it - you re-plastered it in March AND you added a salt water generator to it. You also added borates very recently. Those are three major changes you made to your pool in the course of one swim season so I would expect there to be some significant delta's with your pool water parameters relative to the standard TFP Recommended Ranges.

Your point about what constitutes the "right value" has been the subject of posts in other contexts, such as going below the recommended TA value so as to optimize pH balance. In all of those discussions, at least in my opinion, those pools (including mine) are outliers in terms of water chemistry. My pool, at this point with its high CH, borates, low TA and other parameters is really not representative of your average TFP'ers pool. So there's always going to exist a tension between what is printed in the standard operating methods and recommended ranges of TFP which try to simplify things versus pools like yours and mine which are really not representative of the norm. In other words, our pools represent the 1% of pools out there that need more complicated analysis and our experiences should not dictate changes for everyday folks with everyday, normal pools. "The tail doesn't wag the dog" so to speak....

My 2 cents for what it's worth...
 

chem geek

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Mar 28, 2007
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San Rafael, CA USA
There are a few factors you need to consider. First is that you have an SWG and to prevent scaling in the salt cell it may need a slightly lower than 0 CSI. Maybe with the 50 ppm Borates you are OK and you can judge that for yourself but if you find yourself needing to clean the cell more frequently then you can try targeting a -0.2 CSI instead.

Second is that if you have metals in the water then a higher pH can cause metal staining. If you don't have metals, then you don't need to worry about that.

Third is that the phenol red test kit doesn't test above 8.2 and at 8.2 you can't tell if you're actually higher. If you were going to operate at a higher pH than the test kit can read, you'd need another method of reading pH such as an electronic meter (a more expensive better one) that you baby with keeping its membrane wet and recalibrate it periodically, so obviously this gets more complicated.

Why don't you see about dropping your TA some more to see if that slows down the pH rise in which case you can target 7.8 and not let the pH get above 8.0? That may be more of a sweet spot for your pool. Some people go even lower in TA and while you could experiment with that IF it helps reduce the rate of pH rise, then if you do settle on a lower TA (say 50 or 60 ppm) you'll need to raise the CH some to compensate if this pushes the CSI too negative since you have a plaster pool. You would be out of the Recommended Levels ranges so would need to look at the CSI for what to do in this case (i.e. with a TA lower than recommended so would need a CH higher than recommended).
 

chiefwej

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Jun 12, 2011
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Some of us just can't use the TFP Recommended ranges. If you have fill water with high TA and high CH and rapid evaporation rates like I do, there is no way to keep the CH within range short of drain and refill regularly. Trying to lower TA to control pH rise is also futile. With high TA in the fill water the TA just climbs back up in short order. Watching and tracking my CSI has become a necessity. As the CH continues to rise to, or above 1,000 you have to use the CSI.
 

gilbee

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Mar 31, 2015
300
Harvey, LA
There are a few factors you need to consider. First is that you have an SWG and to prevent scaling in the salt cell it may need a slightly lower than 0 CSI. Maybe with the 50 ppm Borates you are OK and you can judge that for yourself but if you find yourself needing to clean the cell more frequently then you can try targeting a -0.2 CSI instead.

Second is that if you have metals in the water then a higher pH can cause metal staining. If you don't have metals, then you don't need to worry about that.

Third is that the phenol red test kit doesn't test above 8.2 and at 8.2 you can't tell if you're actually higher. If you were going to operate at a higher pH than the test kit can read, you'd need another method of reading pH such as an electronic meter (a more expensive better one) that you baby with keeping its membrane wet and recalibrate it periodically, so obviously this gets more complicated.

Why don't you see about dropping your TA some more to see if that slows down the pH rise in which case you can target 7.8 and not let the pH get above 8.0? That may be more of a sweet spot for your pool. Some people go even lower in TA and while you could experiment with that IF it helps reduce the rate of pH rise, then if you do settle on a lower TA (say 50 or 60 ppm) you'll need to raise the CH some to compensate if this pushes the CSI too negative since you have a plaster pool. You would be out of the Recommended Levels ranges so would need to look at the CSI for what to do in this case (i.e. with a TA lower than recommended so would need a CH higher than recommended).
Thanks Chem Geek---Today's observation was really more of a result of me falling asleep at the wheel over the past couple of days and not applying acid a day sooner when I should have...keeping the pH at 7.8 and staying on top of the rise doesn't look like it's gonna be a big deal especially with the borates giving me a few days in between. What caused my question was when I jumped on poolmath and calculated how much acid to add, I scrolled down the page and saw the CSI of my current levels looked a CSI number that I would normally say is quite good and that made me wonder...

JoyfulNoise posited the same suggestion of lowering TA below 70 to 50 or 60, but I'm not sure I am willing to raise CH to gain the benefit that might bring, especially if I decide to raise TA and revert, then I'm draining water to lower CH or just dealing with it...the local tap water already has a CH of 250-300, so I don't want to rock that boat if I can avoid it.

It sounds like your take is CSI is more influential than the standard levels in the event there's conflict then, am I reading you right? FWIW, I inspected my SWG cell after a month and a half of use and there did not seem to be any scale; I cleaned it anyway, but there really wasn't much in terms of bubbles coming off of it and visually looked very clean, so I think the cell is happy with the balance.
 

bdavis466

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Aug 4, 2014
5,529
San Clemente, CA
Keeping the pool water within the recommended ranges would require very frequent draining and refilling for my area... Not practical.

The CSI is not overly complicated, is very easy to understand, and provides great insight to the overall condition of the pool water in regards to plaster longevity.

Most importantly, the CSI is easily calculated by Pool Math and several apps which take any potential mathematical errors out of the equation.

Why is this always so controversial?
 

chem geek

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Mar 28, 2007
12,083
San Rafael, CA USA
JoyfulNoise posited the same suggestion of lowering TA below 70 to 50 or 60, but I'm not sure I am willing to raise CH to gain the benefit that might bring, especially if I decide to raise TA and revert, then I'm draining water to lower CH or just dealing with it...the local tap water already has a CH of 250-300, so I don't want to rock that boat if I can avoid it.

It sounds like your take is CSI is more influential than the standard levels in the event there's conflict then, am I reading you right? FWIW, I inspected my SWG cell after a month and a half of use and there did not seem to be any scale; I cleaned it anyway, but there really wasn't much in terms of bubbles coming off of it and visually looked very clean, so I think the cell is happy with the balance.
The idea would be that you would lower the TA without changing your CH and determine if it helped or not. Only if you determined that the rate of pH rise was slower at the lower TA would you then increase your CH. You can have a negative CSI for a shorter time. The purpose of preventing plaster degradation is so that you can have plaster last for many years, well over a decade. This is why it is so hard for people to believe it means anything in spite of it being a scientific quantity (based on thermodynamics) because they don't see the negative effects from it corroding plaster unless it's very extreme at low pH. At lesser levels, one needs to examine the plaster under a microscope if only at low CSI for months (such as experiments with plaster coupons that onBalance has done).

The CSI is the actual predictor of whether scaling is possible or dissolving of plaster is possible. It does not predict the rate, but a zero CSI won't scale nor dissolve plaster (one can still scale in an SWCG cell because the pH at the hydrogen gas generation plate is significantly higher than the bulk pool water). The Recommended Levels primarily exist to give a set of ranges to avoid having to calculate the CSI. Otherwise, the ranges could be quite a bit broader for things like TA and CH especially.
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,083
San Rafael, CA USA
Keeping the pool water within the recommended ranges would require very frequent draining and refilling for my area... Not practical.

The CSI is not overly complicated, is very easy to understand, and provides great insight to the overall condition of the pool water in regards to plaster longevity.

Most importantly, the CSI is easily calculated by Pool Math and several apps which take any potential mathematical errors out of the equation.

Why is this always so controversial?
There are those on this forum who VERY strongly believe that new people coming to this site have to see level ranges in a chart and not do a calculation (even if done in PoolMath) to figure out what to do. It's about simplicity and not overwhelming new members. For me, having the pH, CH, TA trilogy balance each other via a CSI calculation (that also includes CYA, temperature, and salt if extra) is not much different than having FC and CYA balanced in a ratio, but as you will note we have a table for FC and CYA, not telling people to use a ratio or FC as a percentage of CYA. If the belief is that new people coming to the forum will resist doing a single division or handling a percentage, you can imagine what would happen if they have to type in at least 5 numbers into a calculator to get CSI. Then you have to explain what to do for each parameter and handle all the various individual circumstances. That would probably lead to a flowchart which could also scare away newbies.

Now there should be some way to bridge the divide between an initial simplistic view for recommendations that apply to many pools into what is needed for a smaller subset of pools though still significant in number (e.g. 10-30% of pools but still a minority). JoyfulNoise and others have proposed some possible modifications or enhancements to the Recommended Levels page and this is still under discussion but nothing has been decided yet.