White Powder on Pool Floor

[natalieh]

Good morning!

I have attached a picture of what has started developing the last several days. Please share your expertise!

Last 3 - 4 weeks pool summary:
Developed what I'm pretty sure was mustard algae after leaving town for a few days and the skimmer sucked in a plastic bag. I know think the algae may have been present prior but with heat and poor circulation, it took off. Performed slam and passed the test. After waiting a couple of days, I hit the pool with 6lbs of pool powder shock ( I have used liquid chlorine all summer, just grabbed this in a hurry) to bring chlorine up to mustard algae level of 34 and then let the chlorine come back down. The last week or so I've noticed a small build up of white powder and I've assumed it was the shock that never dissolved and I keep brushing and stirring it up. I have also had my SWG off for the SLAM process and turned it back on at 50% after passing. Two days ago, i bumped it up to 100%. Yesterday there was more than the usual build up and this morning even more. I turned the swg off yesterday and I added 12 oz algaecide evening as I plan to do an absorbic acid treatment today for stain removal.

We have had numerous days of over 100 degree temp and expect several more this week.

Most recent chemical results. My salt also is rising.

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Chemical Addition 08-22-2023 @ 07:56 AM
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+ 32 FluidOunces of MuriaticAcid29

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Test Results 08-22-2023 @ 07:44 AM
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Free Chlorine: 8.5
Combined Chlorine: 0.5
pH: 7.5
Total Alkalinity: 50
Calcium Hardness: 1200
Salt: 4400
Temperature: 88°F
CSI: -0.13

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Test Results 08-21-2023 @ 09:33 PM
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Free Chlorine: 6.5
Combined Chlorine: 0.5
pH: 7.4
Total Alkalinity: 50
CYA: 80
Salt: 4200
CSI: -0.23

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Test Results 08-21-2023 @ 05:19 PM
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Free Chlorine: 8.0
Combined Chlorine: 0.5
pH: 7.7
CSI: 0.15

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Chemical Addition 08-19-2023 @ 08:11 AM
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+ 33 FluidOunces of MuriaticAcid29

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Chemical Addition 08-19-2023 @ 08:11 AM
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+ 3.5 Ppm of SWG

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Test Results 08-19-2023 @ 07:55 AM
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Free Chlorine: 4.5
Combined Chlorine: 0.0
pH: 7.6
Total Alkalinity: 50
Calcium Hardness: 1150
CYA: 60
Salt: 3600
Temperature: 86°F
CSI: 0.06

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Test Results 08-16-2023 @ 04:16 PM
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Free Chlorine: 23.5
pH: 7.5
CYA: 70
CSI: 0.13

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Test Results 08-15-2023 @ 03:28 PM
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Free Chlorine: 11.0
Combined Chlorine: 0.5
pH: 7.4
CYA: 80
CSI: 0.00

 

[mknauss]

6lbs of pool powder shock

Cal Hypo or dichlor?

Your CH of 1200 ppm and a SWCG will create calcium scale in the SWCG. You need to lower the CH of the pool water.

 

[natalieh]

Cal Hypo

I understand the calcium is high and can cause scaling as well. I work to keep the CSI really low or negative because an alternate water source is not an option, unfortunately.

 

[mknauss]

Cal Hypo is more calcium. And with your water parameters, will cloud the water.

I suspect with that high of CH, the SWCG will create scale regardless what the CSI is. Only way to try and eliminate it is to use borates. That will limit the pH rise in the SWCG cell itself and limit scale creation.

Does your home have a whole house water softener? Using soft water for your pool would make things much easier.

 

[natalieh]

I should have considered the cal hypo being more calcium. That part didn't dawn on me. I am a first year pool owner and I have not looked into using borates. I can check that out.

We have plans to install a whole house water softener. It is a reconstruction home and it is not currently in the budget. Hopefully soon.

Regarding the white powder substance in the pool, are you thinking that it is calcium settling out?

 

[mknauss]

Likely. Gather some of it up and put some acid on it.