Mar 5, 2020
19
Arizona
Hi All,

I've been struggling with rapidly rising CH since my new pool was constructed just over two years ago. Here are my numbers:

In-Ground Plaster Pool 10,000 gallons with startup date of 11/2019. I have a T-9 SWG and Hayward equipment including Acid Feeder and Sense and Dispense system.

Shortly after startup two years ago, a Leslie's CH test showed 275. Now, two years later:

Temp 54
CH: 1125
TA 50
PH 7.7
Salt 3600
CYA 30

I quickly learned to use and trust my Taylor K2005 kit, so haven't used Leslie's since the original CH test. And I use the Pool Math calculator to keep my water balanced... as long as I keep low TA it doesn't seem difficult.

Here are my questions:
1). As long as I keep my water balanced... is there an issue with CH this high (1125)?
2). What could be causing my CH to rise so quickly? I remember after year 1 it had gone to 650 and I was freaking out. Now I know the overall balance is more important, and so I focus on that... but still 1125 is freaking high after only two years!

Any thoughts or suggestions? I'd rather not drain the pool if the CSI balance is all that is important, but I'm nervous about the CH number.

Thanks!
 

ajw22

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1125 is up where you can't use low pH and other water chemistry adjustments to keep out of the scaling level. I think it is time to drain your pool and lower the CH.

Your high CH water used to replace evaporation causes your CH to rise. Using softened water to fill your pool can prevent the need to periodically drain.

@mknauss is in your area and can discuss this more.
 
Mar 5, 2020
19
Arizona
1125 is up where you can't use low pH and other water chemistry adjustments to keep out of the scaling level. I think it is time to drain your pool and lower the CH.

Your high CH water used to replace evaporation causes your CH to rise. Using softened water to fill your pool can prevent the need to periodically drain.

@mknauss is in your area and can discuss this more.
Well... that's really the root of my question. Even though I can still easily balance the water with TA and PH within recommended range... it still isn't advised? I felt like I was missing something assuming that overall balance is the only factor, so still trying to figure out where the unhealthy range is for any single component, such as CH, even within an overall balanced water chemistry.
 

mknauss

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Elevated CH is not unhealthy to you. But it can be to your pool surface when scale starts to form. Removing that scale can be detrimental to your plaster surface.
 

mknauss

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Pretty difficult to have a negative CSI at that level of CH, at least for very long. But yes, you will get scale, especially at the water line, regardless that your CSI is that low. Evaporation at the waterline will leave behind scale.
 
Mar 5, 2020
19
Arizona
Pretty difficult to have a negative CSI at that level of CH, at least for very long. But yes, you will get scale, especially at the water line, regardless that your CSI is that low. Evaporation at the waterline will leave behind scale.
So, what am I doing wrong with my CSI calculations, then? (Using Pool Math BTW). When I look at my numbers, I see lots of room for lowering PH, or increasing CYA to maintain a slightly negative balance when the water temps rise to the usual max of around 84 here in AZ. I am seeing some scaling at the water line, to your point, but nothing on the plaster that I can see. Am I missing something in the balance concept?

Temp 54
CH: 1125
TA 50
PH 7.7
Salt 3600
CYA 30
 

mknauss

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Water temperature is driving the CSI low. Change that to 88F which is normal for June on. Also a TA of 50 is very hard to maintain with our fill water as the TA of the fill water is 130 ppm.
 
Mar 5, 2020
19
Arizona
Yes, summer will be more challenging for sure. I have started to notice the dreaded white flakes in the pool last summer, so I guess the water simply can't hold any more calcium, and that may be the limiting factor more than overall balance. Thanks for the help, Marty!

Allen... I'm using the Taylor K2006 kit. 45 drops for CH yields the 1125 number.
 

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Mar 5, 2020
19
Arizona
Hey just thought of my last question. Could a bad plaster mix be causing the rapid rise in CH over the two years since the pool was built? Trying to figure out where else the calcium is coming from? Fill water isn't that high to drive the number up that high in just two years I don't think. I'm at the end of my warranty, so if plaster could be a factor, I should reach out to the builder now.

Thanks
 

Rancho Cost-a-Lotta

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My fill water CH is 125. Looking back at my logs, CH rose from 425 to 600 (about 40%) during a one year period. Not sure if it helps, but assuming the numbers are accurate, your CH rise seems excessive. Let us know the results of the updated fill water test.
 
Mar 5, 2020
19
Arizona
So I just rechecked my fill water and the CH is 90ppm. So, still questioning what is causing the 2-year rise from 275 to 1125 CH, as that 90 fill water wouldn't really do it would it? We did get a lot of rain last monsoon season, but I would think that would lower it rather than raise it. Curing plaster during the first year could raise it, but from 700-1125 in the second year has me still wondering if a bad plaster mix may be the culprit, but please weigh in on fill cycles over a two year period in AZ, and how much 90ppm would typically raise the CH level?

Thanks!
 

mknauss

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Your water source must be much different than the bulk of the Phoenix area. Colorado river water is 250 ppm CH at the source.
 

Leebo

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Something is very odd with your numbers,

Shortly after startup two years ago, a Leslie's CH test showed 275. Now, two years later:

I remember after year 1 it had gone to 650 and I was freaking out.

I am seeing some scaling at the water line, to your point, but nothing on the plaster that I can see.

I suspect everybody here suspects the current test of 1125 to be correct, and I suspect all of us are also guessing it’s from your fill water. While new plaster does increase CH slightly I’d be somewhat shocked if it raised it that much. A few questions quickly come to mind,

  • How are you testing your fill water?
  • Do you use CalHypo to help chlorinate?
  • How often do you need to add acid during the summer?
  • What is the TA of your fill water?
 
Mar 5, 2020
19
Arizona
Something is very odd with your numbers,







I suspect everybody here suspects the current test of 1125 to be correct, and I suspect all of us are also guessing it’s from your fill water. While new plaster does increase CH slightly I’d be somewhat shocked if it raised it that much. A few questions quickly come to mind,

  • How are you testing your fill water?
  • Do you use CalHypo to help chlorinate?
  • How often do you need to add acid during the summer?
  • What is the TA of your fill water?
Sure... here are the answers:
  • Testing fill water from the spigot where the auto fill is tee'd. Testing using K2006 CH test. Fill water at 90ppm
  • No, the only chlorine that is used post the initial start-up two years ago is the SWG, and a total of two gallons of liquid chlorine when I had SWG issues on the sense and dispense. The startup consisted of Shock, Conditioner, MA, and several Chlorine pucks(so maybe that was CalHypo?)
  • The pool drinks acid like crazy. I go through 1-gallon every 3-4 weeks on average. Summer every 3 weeks, and winter every 4-5 weeks. Actually posted about that a year ago, as it was a concern to me, but members seemed to think it wasn't unusual.
  • TA of the fill water is 120; For kicks I measured PH of fill water as well, and it's 8.0. Since I have a Spa / spillover, the water is aerated somewhat through that system, and I suspect that generates the higher PH and drives acid demand a bit. Because of that, my TA tents to drop over time, and I keep it around 50 with the addition of baking Soda, to provide room to manage balance, given my rising CH numbers.
What are you seeing that is very odd with the numbers, other than the high CH?
 

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