CSI is below 0.6 - cause for concern?

[ak29]

Hi,

The CSI reading below was 0.7 a couple weeks ago when the PH was mid 7s. I had just added acid. I am curious if this is something to be concerned about or nothing. Until the weather cooled off CSI was close to 0.

Latest Test Result Summary:
FC: 8.0 (13 minutes ago)
CC: 0.0 (13 minutes ago)
pH: 7.9 (13 minutes ago)
TA: 60 (3 days ago)
CH: 325 (3 days ago)
CYA: 70 (2 months ago)
SALT: 2500 (3 days ago)
BORATES: 40 (4 months ago)
TEMPERATURE: 55° (13 minutes ago)
CSI: -0.61 (13 minutes ago)

Thanks

 

[mas985]

Hi,

The CSI reading below was 0.7 a couple weeks ago when the PH was mid 7s. I had just added acid. I am curious if this is something to be concerned about or nothing. Until the weather cooled off CSI was close to 0.

That is -0.7 correct?

Latest Test Result Summary:
FC: 8.0 (13 minutes ago)
CC: 0.0 (13 minutes ago)
pH: 7.9 (13 minutes ago)
TA: 60 (3 days ago)
CH: 325 (3 days ago)
CYA: 70 (2 months ago)
SALT: 2500 (3 days ago)
BORATES: 40 (4 months ago)
TEMPERATURE: 55° (13 minutes ago)
CSI: -0.61 (13 minutes ago)

Thanks

I entered the above numbers and got a CSI of -0.49, not -0.61.

I wouldn't be too concerned. I had mine less than -0.6 for several weeks at a time without any issues and my plaster is over 18 years old. Short durations of very low CSI will not have a significant impact on the plaster.

However, why are you adding acid if CSI is that low? Because of the PH?

 

[key1cc]

You report CSI as -0.61 but when i plug your numbers in I get -0.51....I'm using the free "Pool Math" app maybe that's the difference....

To answer your question....The ideal range for csi is -0.3 to +0.3 but acceptable range extends up to -0.6 to + 0.6 (you just can't leave it outside the ideal range indefinitely or you risk issues.) In your case, I would think the more negative you go past -0.6 (or -0.3 for that matter) the sooner any potential issues would develop.

 

[ak29]

> That is -0.7 correct?

Ah yes, I forgot to sign it.

I entered the above numbers and got a CSI of -0.49, not -0.61.

I wouldn't be too concerned. I had mine less than -0.6 for several weeks at a time without any issues and my plaster is over 18 years old. Short durations of very low CSI will not have a significant impact on the plaster.

However, why are you adding acid if CSI is that low? Because of the PH?

I had the TA down as 55, but I think it's meant to be rounded to 60. That small change produces -0.51 CSI.

I put acid in 3 weeks ago as the PH was 8.2 or more. The cooler weather (and maturing plaster) + no SWG running seem to reduce the acid demand but haven't removed it entirely.

The numbers do not seem dramatically different from earlier in the year but the CSI number stands out. I'll have to add acid in a few weeks and if it hits mid 7s in the pH that'll come with a CSI dip, based on a static analysis...

Calcium should be fine at 325, is it worth adding more?

 

[Bperry]

Ah yes, I forgot to sign it.

I had the TA down as 55, but I think it's meant to be rounded to 60. That small change produces -0.51 CSI.

I put acid in 3 weeks ago as the PH was 8.2 or more. The cooler weather (and maturing plaster) + no SWG running seem to reduce the acid demand but haven't removed it entirely.

The numbers do not seem dramatically different from earlier in the year but the CSI number stands out. I'll have to add acid in a few weeks and if it hits mid 7s in the pH that'll come with a CSI dip, based on a static analysis...

Calcium should be fine at 325, is it worth adding more?

What test kit are you using? There’s no rounding of test results other than CYA.

 

[jimbethesda]

Calcium should be fine at 325, is it worth adding more?

What’s the calcium concentration of your fill water? I see you’re in Fort Worth, so not unusually high rainfall.

Here in Austin, lots of evaporation leads to gradually increasing calcium. If you are using calcium-free water, then might be good to add a little. If you‘re like most of us, your calcium will increase over time.

 

[mas985]

I agree with the above. I would not add calcium in your location. You would be better off just running at a higher PH until water temps increase.