What is most important to prevent scaling ph or csi?????????

[RESISTENCIA13]

I puzzled and need some guidance as to what is most important to prevent calcium scaling. Last year I closed my pool with the following readings:

Water Temperature 61
FC 21.5 As I slammed before closing
PH 7.4
TA 70
CH 575
CYA 60
Salinity 3000
CSI -0.39

When I opened my pool I had scaling. However, my reading at opening were as follows:

Water Temperature 53
FC 0
PH over 8.4 based on the PH test scale
TA 120
CH 500
CYA 60
Salinity 2900
CSI 0


So yes, my PH went above 8 PPM, but the CSI was 0. I was told when closing my pool on this forum that as long as CSI was between 0.6 and -0.6 the high CH would be ok. Any thoughs would be really appreciated.

 

[bdavis466]

Your CSI was not 0, It was well above +0.6. How did you come to that CSI level?

I figure if your pH was 8.4 then the CSI would have been around +0.76 which is easily in the scaling range. Given your TA of 120, your pH was likely much higher than 8.4 which would further lead the CSI upward.

PH is the biggest driver of CSI and should be given most of the attention but all of the parameters that you test do have an impact on the results, water temperature included.

 

[jblizzle]

If I put your numbers in PoolMath ... I do not get a CSI of 0 ... I get 0.75 ... not sure what you were looking at.

I can not get PoolMath to get me a CSI of 0 with out of whack numbers.

 

[JoyfulNoise]

Are you still using pH-Minus to lower pH?

 

[RESISTENCIA13]

Are you still using pH-Minus to lower pH?

No. I graduated and learn my lesson. Now I used acid.

 

[bdavis466]

I can not get PoolMath to get me a CSI of 0 with out of whack numbers.

I have had it give me incorrect CSI values on occasion but couldn't track down the reasoning.

 

[JoyfulNoise]

Where is the scaling? What does it look like?

We've had a number of threads from over-wintered east coast pools that showed scaling problems. Seems to be a major issue with plaster pools and cold winters. The pH gets too high and then scale forms. Calcium carbonate (and many other calcium salts) have what's called retrograde solubility - calcium is more soluble in colder water than warmer water. So I would hazard a guess that a plaster pool in the cold east coast winters is going to have more issues with scaling than other types of pools.

Honestly, I really thought pools back east were either fiberglass or vinyl. Growing up in NY I don't think I ever saw a plaster pool.

 

[RESISTENCIA13]

I used a phone application called Poolpal (like pool math on a phone). Since PH was above the reading levels I used 10PPM and it gave me 0. I used the same numbers in pool math and is giving me a PH error. So it looks like my application gave me a o instead of a PH error like pool math. Well, now I know that I cannot trust the application at all times. My current chemical level are as follows and I notice that the higher the PH and AK the better the CSI

Water temperature 80
FC 7
PH 7.4
AK 80
CH 300
CYA 80
Salinity 3000
CSI -0.46

If I lower the TA 70 it increases my CSI. If I increase my PH it lower my CSI. Why? I though the lower I have my PH and AK the better my CSI will be, but pool math show me differently.

- - - Updated - - -

Where is the scaling? What does it look like?

We've had a number of threads from over-wintered east coast pools that showed scaling problems. Seems to be a major issue with plaster pools and cold winters. The pH gets too high and then scale forms. Calcium carbonate (and many other calcium salts) have what's called retrograde solubility - calcium is more soluble in colder water than warmer water. So I would hazard a guess that a plaster pool in the cold east coast winters is going to have more issues with scaling than other types of pools.

Honestly, I really thought pools back east were either fiberglass or vinyl. Growing up in NY I don't think I ever saw a plaster pool.

We have lots of plasters pools around here. Most people I know have plaster....some have vinyl, but above ground. See attached pictures of the scaling. I emptied and tried acid washing, but did not see much coming off so I stopped. Might tried when closing it. If I still own the house, as I will be moving soon and will make sure to get a fiberglass pool next time.

 

[jblizzle]

Lowering the TA and pH is not increasing the CSI, it is making it more negative as expected.

 

[RESISTENCIA13]

Lowering the TA and pH is not increasing the CSI, it is making it more negative as expected.

Yes, it's making it more negative. I meant to said above the recommend it range on the negative side. My point if I lower my TA it shall make it less negative towards the favorable range to avoid scaling.

 

[jblizzle]

I think you are confused, or I do not understand what you are saying.
You can not be "above the recommended range on the negative side"

Scaling will occur if the CSI > +0.6

If your CSI is negative (<0) then you will not get scaling.

Lowering the TA or pH will lower the CSI ... towards negative infinity.
If you started at +0.5 say it will drop to say +0.3
If you started at -0.5 say it will drop to say -0.7

 

[RESISTENCIA13]

Jason,

Thanks for the explanation. You are right! I was deeply confused and misreading my CSI.

I think you are confused, or I do not understand what you are saying.
You can not be "above the recommended range on the negative side"

Scaling will occur if the CSI > +0.6

If your CSI is negative (<0) then you will not get scaling.

Lowering the TA or pH will lower the CSI ... towards negative infinity.
If you started at +0.5 say it will drop to say +0.3
If you started at -0.5 say it will drop to say -0.7