High CSI - What to do?

Cwiggs

Well-known member
Aug 31, 2019
118
Phoenix, AZ
Hello TFP,

So It's hot here in Phoenix, really hot, I think the high yesterday was 118F O_O. I think I have the water mostly balanced, however my CSI is pretty high and I'm worried it's going to cause scaling.

I think my fill water has high TA, so the TA is always going to be creeping up, not 100% on this though. For the last few months I've been putting in ~32-64oz of 31.45% MA in the pool about once a week to keep the PH and TA down, however my TA has been hovering around 90-100ppm for a while. I haven't tried to lower it more because I've read a lot of posts saying it will go down on it's own over time and that 90-100ppm isn't too bad anyway. However now I'm wondering, with a combination of the pool water being high, and the high pH/TA at the end of the week, is that making the CSI too high as well.

So my thought is that I should lower my TA to around 60ppm (while keeping pH around 7.6, using the aeration method, etc) that way, even if my pH gets to around 8.0 for a couple days the CSI will still be in the lower range.

You can check my poolmath logs in my profile, but here is my most recent chemical tests:
FC - 6.5
pH - 8.2 (Put in 64oz of MA after this was taken)
TA - 90
CH - 475 (taken 1 month ago
CYA - 50 (15 days ago)
Temp - 87F
CSI - 0.82

What are your thoughts?
 

Cwiggs

Well-known member
Aug 31, 2019
118
Phoenix, AZ
Play with pool math, enter different results as if they were real to see what changes and how much.
Playing with the app and it leads me to the same conclusion. If I have my TA at 60, pH at 7.6 and the temp is around 87 the CSI is 0. That leaves me a lot of buffer on the CSI. Better yet if my TA is 50, my pH can go up to 8.2, and temp of 87, and my CSI will be -0.11. So it really sounds like I should slowly lower my TA. But I'd love to see what others think.
 

Oly

Gold Supporter
Jun 28, 2017
1,676
Fresno, CA
Double check your pool math numbers, I can't recreate your CSI estimations using your numbers in the web version of Pool Math. :scratch:
 

proavia

LifeTime Supporter
TFP Guide
Feb 6, 2015
1,990
Chandler AZ
Adjust you pH as often as necessary. Adjusting only once a week or so just isn't enough. With our high evaporation rate and 130-ish TA refill water you need to be more proactive. Test everything more fequently in the heat of summer - maybe less frequently in winter.

If your CH was 475 a month ago, it is almost certainly over 500 by now. In summer, test CH twice monthly to see a better trend. Chances are you have added over 1 foot of fill water in the last month.

Bring your pH down to 7.2 to help aid in lowering your TA. No real need to aerate, just let the pH rise on its own. Don't let the pH rise all the way to 8+ before adding acid again. Shoot for a TA of 60 or 70 and look at PoolMath to see where pH should be to keep your CSI between 0.00 and -0.30 .
 
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Cwiggs

Well-known member
Aug 31, 2019
118
Phoenix, AZ
Adjust you pH as often as necessary. Adjusting only once a week or so just isn't enough. With our high evaporation rate and 130-ish TA refill water you need to be more proactive. Test everything more fequently in the heat of summer - maybe less frequently in winter.

If your CH was 475 a month ago, it is almost certainly over 500 by now. In summer, test CH twice monthly to see a better trend. Chances are you have added over 1 foot of fill water in the last month.

Bring your pH down to 7.2 to help aid in lowering your TA. No real need to aerate, just let the pH rise on its own. Don't let the pH rise all the way to 8+ before adding acid again. Shoot for a TA of 60 or 70 and look at PoolMath to see where pH should be to keep your CSI between 0.00 and -0.30 .
Okay, I'll test more frequently moving forward.

I've been bringing the pH down to around 7.2 for months without aerating, however my TA is still slowly increasing, so it seems if I want to get it down I need to put in MA, and aerate more often to get the TA to 60 or 70. Once the TA is around 60 to 70 I won't be aerating anymore.

Does that sound like a good plan?

I'll go run some more tests on the pool and mess with PoolMath more and report back.

Thanks again for everyone's help!
 

proavia

LifeTime Supporter
TFP Guide
Feb 6, 2015
1,990
Chandler AZ
Adding acid lowers pH and TA. Aerating raises pH without raising TA. If you want to lower the TA quicker, aerate to raise the pH and then lower again to lower the pH and TA. As the TA comes down, you will notice the pH rises more slowly. Plug some numbers into PoolMath to see how changes in TA, pH and CH affect theCSI outcome.

Also, if you haven't replaced all the pool water via drain/refill in a couple of years, your salt level is probably in the 1000-1500 range. This will affect CSI a bit too.

BTW - your CH of 475 shows a test date of two months ago. Time to test that again to get a valid number.
 

Cwiggs

Well-known member
Aug 31, 2019
118
Phoenix, AZ
Double check your pool math numbers, I can't recreate your CSI estimations using your numbers in the web version of Pool Math. :scratch:
Ah, you are right, I must have messed something up.

Adding acid lowers pH and TA. Aerating raises pH without raising TA. If you want to lower the TA quicker, aerate to raise the pH and then lower again to lower the pH and TA. As the TA comes down, you will notice the pH rises more slowly. Plug some numbers into PoolMath to see how changes in TA, pH and CH affect theCSI outcome.

Also, if you haven't replaced all the pool water via drain/refill in a couple of years, your salt level is probably in the 1000-1500 range. This will affect CSI a bit too.

BTW - your CH of 475 shows a test date of two months ago. Time to test that again to get a valid number.
I think the "issue" with the TA lowering on it's own over time where I am located is the TA from the fill water is just too high, so it'll very slowly just rise until I add more MA than normal and aerate to increase the pH.

I emptied the whole pool at the end of December 2019 so my salt level shouldn't be too high. But I'll take that into account.

I just re-tested and here are the numbers:
pH - 7.1
TA - 80
CH - 500
CYA - 50 (close to 40 but I know we round up)
CSI - -0.29

So after the MA my CSI looks good but you are right that i'll probably need to add MA twice a week.

A few questions (especially for anyone in PHX)

* I assume the CH in Phoenix is just high so my CH will just continue to rise. Eventually will I just need to do a drain and re-fill?
* Should I be keeping my CYA higher than 50 since the summers in AZ are brutal?
 

proavia

LifeTime Supporter
TFP Guide
Feb 6, 2015
1,990
Chandler AZ
With our high evaporation here in the Valley of the Sun, I have been adding acid twice a week - but my CH is over 900, TA 70 and I am keeping pH in check to try to keep CSI in check. A drain will be coming this fall or spring - and a new fill line from the water softener. Now to talk the CFO (wife) into a SWG to go along with the water change and soft water make up line.

Phoenix reports an average hardness of 14.9 grains - about 255 ppm
Chandler reports an average hardness of 16.5 - about 280 ppm
I think that is calcium, magnesium and maybe other things - but the calcium is the greater of them. Test your pool make up water and find out what the CH, TA and pH are.

Once you get your TA down in the 70-ish range, it will be easier to keep it there.

No matter where you live, when water evaporates from your pool the CH stays behind. And in PHX we evaporate at least our entire pool every year - so our CH might start at 250, but in a year or less is at 500 and 750 the following year (and that is only taking into account evaporating your entire pool volume in a years time - we may evaporate more than that). The higher the pan evaporation rate, the quicker the CH climbs. I would guess we lose 75-100 inches of water to evaporation a year.

I usually keep my CYA at 50. That allows me to float 3" tabs if I go away for more than a few days. If I do use tabs, I have a little wiggle room on the CYA. I guess this year - given the present situation - I probably should have upped the CYA to 60. I use about 24-32 oz of 12.5% per day in my 12300 gallon pool. I would think you use twice that much in your 21k pool.
 

Cwiggs

Well-known member
Aug 31, 2019
118
Phoenix, AZ
With our high evaporation here in the Valley of the Sun, I have been adding acid twice a week - but my CH is over 900, TA 70 and I am keeping pH in check to try to keep CSI in check. A drain will be coming this fall or spring - and a new fill line from the water softener. Now to talk the CFO (wife) into a SWG to go along with the water change and soft water make up line.

Phoenix reports an average hardness of 14.9 grains - about 255 ppm
Chandler reports an average hardness of 16.5 - about 280 ppm
I think that is calcium, magnesium and maybe other things - but the calcium is the greater of them. Test your pool make up water and find out what the CH, TA and pH are.

Once you get your TA down in the 70-ish range, it will be easier to keep it there.

No matter where you live, when water evaporates from your pool the CH stays behind. And in PHX we evaporate at least our entire pool every year - so our CH might start at 250, but in a year or less is at 500 and 750 the following year (and that is only taking into account evaporating your entire pool volume in a years time - we may evaporate more than that). The higher the pan evaporation rate, the quicker the CH climbs. I would guess we lose 75-100 inches of water to evaporation a year.
Hm, very interesting, so without a water softener filling the pool, at least in the PHX area we will have to replace the water about every 3 years if we want to keep the CH in check.

I usually keep my CYA at 50. That allows me to float 3" tabs if I go away for more than a few days. If I do use tabs, I have a little wiggle room on the CYA. I guess this year - given the present situation - I probably should have upped the CYA to 60. I use about 24-32 oz of 12.5% per day in my 12300 gallon pool. I would think you use twice that much in your 21k pool.
Gotcha, I've been keeping my CYA at 50 as well, but I wasn't sure if I should have it higher since it's so hot here. Someone on the TFP in another post mentioned I might want CYA around 70-80ppm. Yeah you are about right, I've been putting in about 64oz of 12.5% per day

Thanks for all the info, it's helpful to get some info from someone living in the PHX area since we have such brutal summers.