White flakes in plaster pool with lower CH

Jul 2, 2021
5
Seattle
Pool Size
20000
Surface
Plaster
Chlorine
Liquid Chlorine
Newly managing a pool after giving up on my pool service company a month ago. For the past year I've seen white flakes in the pool - they are visible in the sun when the pool otherwise looks very clear. I also have many CH nodules on the bottom and side of the pool but I don't notice scaling.

After I took over managing the pool I upped the CH from 175 to 250, and I'm wondering if I should continue pushing it up to 350 and if that's the likely cause of the issue. I have seen that low CH may cause the leaching but I want to confirm the next steps before I add more calcium.

Specific questions:
1. Are the flakes caused by calcium leaching from the plaster?
2. Is raising the CH the right step to address these?

Test results:
FC: 4
pH: 7.6
TA: 120
CH: 275
CYA: 30
CSI: 0.19
Temp: 89
Pool passes OCLT

Chlorine pool / 20k gallons / Plaster

Pool log from Pool Math:
 
Last edited:

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
43,982
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Welcome to the forum!
You would not have calcium scale flakes in your pool with that water chemistry. Only caveat to that would be if you have a SWCG, which you do not show in your signature.
From your Poolmath logs, you have been adding quite a bit of calcium. Be sure you space the additions out. Also your high TA could be keeping some of the calcium chloride from readily dissolving.
I suggest you read ABC's of Pool Water Chemistry
 
Jul 2, 2021
5
Seattle
Pool Size
20000
Surface
Plaster
Chlorine
Liquid Chlorine
Thanks for the responses!

@mknauss, good to know this is unlikely to be calcium scale flakes. They were there prior to adding calcium but good to know to watch for dissolving issues. So far I've spread out the additions over multiple days with no problems.

@YippeeSkippy, the specks are so small I can't grab them with my hands (I should call them specks rather than flakes given the size). What were you thinking they might be if they responded to vinegar?

Attaching a photo of what it looks like - they are very small specks and only visible in bright light against a dark background. Otherwise the pool looks very clear given their small size and relatively small number per volume.
 

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ManiacalMama

Well-known member
Jul 18, 2017
171
Antelope, CA
In your signature it says "covered". What does that mean?
I keep a solar cover on our pool most of the time. The water that evaporates on top of it causes a calcium scale to develop. When I pull the cover back for swimming it dumps some calcium flakies into the water. I run the filter for a couple hours after and it clears it (mostly) up.
 
Jul 2, 2021
5
Seattle
Pool Size
20000
Surface
Plaster
Chlorine
Liquid Chlorine
@ManiacalMama very interesting! Yes I have a vinyl Coverstar rolling cover that is over the pool at all times I’m not using it. Since I don’t have the pool open for more than 2 hours at a time it’s possible the flakes could be coming from the cover each time as you experience.
 
Jul 2, 2021
5
Seattle
Pool Size
20000
Surface
Plaster
Chlorine
Liquid Chlorine
@YippeeSkippy , I run the pump 18
hours a day (enough to keep the temp I need) though I also experienced the specks when running it 24/7.

Thanks for the tip about DE!
 

ManiacalMama

Well-known member
Jul 18, 2017
171
Antelope, CA
@ManiacalMama very interesting! Yes I have a vinyl Coverstar rolling cover that is over the pool at all times I’m not using it. Since I don’t have the pool open for more than 2 hours at a time it’s possible the flakes could be coming from the cover each time as you experience.
When it's really warm out I will leave the cover off for a couple days. When I do that I notice the water clears up perfectly.
Your CH isn't that high (mine is 650) but it could still be just enough to build up on the cover.
Have you noticed any white watermarks/scaling on top or around the edge of the cover?
 
Jul 2, 2021
5
Seattle
Pool Size
20000
Surface
Plaster
Chlorine
Liquid Chlorine
@ManiacalMama yes I have a few tiny holes in the cover that leak water out to the top of the cover, and I see some scaling on the top as the water leaks through and dries.
 

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ManiacalMama

Well-known member
Jul 18, 2017
171
Antelope, CA
@ManiacalMama yes I have a few tiny holes in the cover that leak water out to the top of the cover, and I see some scaling on the top as the water leaks through and dries.
A little further reading made me realize, in your case, it could be salt instead of calcium. Either way I don't think it's anything to really worry about, as long as your filter can catch it.
 
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