Calcium Crystals? or Scale?

[cmdonnel]

HI James, during the summer, yes.. I was brushing with a combo brush (steel and plastic bristles) at least once a week, probably more like twice. All summer the water was crystal clear and plaster remained super smooth.. no calcium deposits or any issues. Since the pool has been closed I have not been brushing.

Sorry about my note, I was saying I added TA-Up to bring it up from 70 to 90. The way my Ph was always rising I anticipated a rise over the winter so wanted my TA up a little higher (from 70 to 90) to anticipate the eventual decrease with added MA over the winter. But, as it turns out, without the SWG running, the Ph has been dare near perfectly stable.. so I actually havent added anything since closing and the TA has remained at 90.
My notes in the left-hand column are stating what I did PRIOR to that row's test results.

 

[onBalance]

How certain are you that new crystals are forming? I note a photo that you posted labeled "precipitate." Is that some calcium chloride prills that you added to raise the calcium level or something else?
Does your pool have a spa? Just asking for considering to perform a test.

 

[cmdonnel]

Hi onBalance.. thanks for taking a look at this thread.
I’m positive the crystals are new. The pic labeled 1_5 was just taken and those little white “bumps” just formed in this last week between checks. I’ve been pulling back the cover, circulating the water with the sumps (1-2 hrs) and testing the water every week and they weren’t there earlier in December.
The precipitate is stuff that appears to have settled out of the water, probably from the circulating water washing it off the walls. I have not added anything granular to the pool.
There is no spa , just the pool.
Right now the calcium crystals/bumps can be brushed off… but I haven’t fully taken off the cover to do that.

 

[onBalance]

Yes, I see the white crystal bumps in the left photo (1_5_ 2025) in post #33. What about the photo on the right side (1_5_Precipitate), which does not look like sharp crystals.

I believe "calcium sulfate" should be ruled out because of the result of your fizz test.
I think it is time to consider poor plaster quality as a possible issue which is addressed in my article "Why Are Calcium Crystals Forming in Pools."
What I don't understand is why this problem didn't also occur during the first two winters after your pool was completed.
Any thoughts on that?

 

[cmdonnel]

Yes, I see the white crystal bumps in the left photo (1_5_ 2025) in post #33. What about the photo on the right side (1_5_Precipitate), which does not look like sharp crystals.

I believe "calcium sulfate" should be ruled out because of the result of your fizz test.
I think it is time to consider poor plaster quality as a possible issue which is addressed in my article "Why Are Calcium Crystals Forming in Pools."
What I don't understand is why this problem didn't also occur during the first two winters after your pool was completed.
Any thoughts on that?

I just ordered this test (Amazon.com) to test the sulfate level of the water. It will be here today and I will measure tomorrow once the snow clears.
The precipitate is something new this year... I didnt experience that last year. If you happened to view the video, you'll see a bunch of white "stuff" flowing thru and I believe that precipitate is calcium that was pushed off the walls elsewhere in the pool and just settled on that step once I turned off the sump pumps.
I have read the article you mentioned.. I think I've read every article and forum on this topic (alarmed to see how many there are) and am still so lost on actual root cause.
Regarding timing, the only rationale I can fathom is that when the pool was drained and polished in Spring 2023 (the first time) due to the plaster being over-exposed, it weakened the plaster and allowed bond failure or nodules to then break thru that following winter. When I closed my pool in the winter of 2023 my Calcium was pretty low (around 150) so I believed what I was told that the calcium was leached from the plaster over the winter, and then hardened with the rising Ph and water temps in the spring. But this winter... I'm lost. My calcium has been 400+, and my Ph has been steady.
I just reached out to the National Plasterer's Association to see if they could investigate and analyze. It's close to $5K every time I have to drain and polish the pool so willing to pay whatever it takes to stop this process.

 

[onBalance]

Unfortunately, I believe the only remedy to deal with this problem is to somehow brush the pool and probably with a stainless steel brush instead of nylon.
And unfortunately, the only way to determine or prove that the plaster itself is defective is by taking a "core sample" of the plaster and having it analyzed for its' calcium chloride content.
It would be nice if the NPC would actually and honestly investigate this issue, but I doubt they will do so.

 

[cmdonnel]

Regarding the core sample.. I’ve seen you mention that in other posts.. taking a couple inch sample of the plaster. I guess I could use a chisel and take some out but what kind of damage does that do to the surrounding plaster or gunite?

 

[cmdonnel]

Sorry, one more thing.. the pool
Builder actually said they would investigate once the pool is uncovered in the spring, but they also said they will likely start with an acid wash… thoughs on that? I know that won’t solve the underlying problem, but could that do more damage than good?

 

[onBalance]

If the builder performs a very light (diluted) acid wash, that wouldn't cause too much harm.
Each year that passes means that it is less likely that this problem will occur during the next winter.
I dislike having some plaster chipped out and removed unless it will achieve a desired and productive outcome. Patching up the plaster afterwards never looks good.

I hope you can educate the builder so that he decides that it is in his best interest to supervise the plastering of his pools in the future. He needs to ensure that very little calcium chloride is added to the plaster mix and slow down the speed at which a plaster pool is completed. Plasterers should take an hour or two longer to do the plastering job right.

 

[cmdonnel]

If the builder performs a very light (diluted) acid wash, that wouldn't cause too much harm.
Each year that passes means that it is less likely that this problem will occur during the next winter.
I dislike having some plaster chipped out and removed unless it will achieve a desired and productive outcome. Patching up the plaster afterwards never looks good.

I hope you can educate the builder so that he decides that it is in his best interest to supervise the plastering of his pools in the future. He needs to ensure that very little calcium chloride is added to the plaster mix and slow down the speed at which a plaster pool is completed. Plasterers should take an hour or two longer to do the plastering job right.

Thanks on balance… I will let you know the results of the sulfate test too.
For future reference, did you see anything wrong with my current water chen results? Should I try to keep my CH lower? Or as long as the CSI is balanced between CH and PH and other inputs I’m good?

 

[onBalance]

Your current water balance is very good. I wouldn't change a thing.

 

[cmdonnel]

@onBalance , have some more data points to help with the problem identification.
Sulphates came back as 0.
Phosphates continue to be very high (this is according to Pool Store, I dont have a Taylor test kit for that): 3000-4000 range

Water chemistry remains stable:
Water Temp 34
Ph: 8.2 (this is a little higher than I wanted so I added 2 cups of Muriatic Acid to bring this down per Pool Math)
TA: 90
CH: 450
Salt: 3000
No Borates

I removed the majority of the pool cover (different sections at a time) and noticed there was a bunch more precipitate on the sunShelf. I captured some more pieces in a solo cup and got some better pictures (included). I also took a video of the pieces on the sun shelf. I added some muriatic acid to the pieces in the cup and there was no fizzing, they just dissolved.

In a different shallow section of the pool I also noticed there was a ton of precipitate that was settled on the bottom of the pool. When I brushed it, it immediately "poofed" into a white cloud. You can see this in the video below called "brushing". This seems to match other videos of calcium precipitate.

So my next question is, if this is calcium... what would cause the calcium to fall out of solution like that? I said my pool company accidentally overdosed the pool with Jacks Magic Purple Stuff before closing (which caused the high phosphates), but that should help KEEP things in solution. Some may consider my CH "high", but my numbers are right in line when calculating CSI per pool math. So if my CSI is in check and I have an abundance of sequestrant in the pool..what am I missed that would cause this issue?
The only plus side to this year's fiasco is that it doesnt seem to be hardened onto the pool surfaces yet. I'm hoping the sump pump water movement and brushing (probably wont be able to do it again till early Spring at this point with the water beginning to freeze) will stop it from hardening.

 

[JamesW]

I added some muriatic acid to the pieces in the cup and there was no fizzing, they just dissolved.

Calcium Carbonate would fizz.

Other forms of calcium will not fizz like calcium phosphate.

It might be calcium phosphate.

Maybe try reducing phosphates with phosphate remover.

 

[PoolStored]

Put the crystals in vinegar, if they fizz then they are calcium carbonate. If they do nothing but seem to very, very, very, imperceptibly dissolve, then it's calcium sulfate.

If you can take the crystals and put them in concentrated MA and they still do nothing, then it's calcium phosphate scale.

 

[cmdonnel]

Thanks guys. The calcium definitely dissolved, but didnt fizz. I thought it might be calcium sulfate, but my sulphate level was 0 according to a recent test (could only find test strips to perform this test).
Reading about calcium phosphate, that stuff scares me! The high phosphate level (4000 ppb or maybe higher) def leads me down that path, but I keep reading it starts to precipitate at HIGHER temps and high ph. My water is currently 34 degrees and Ph is about 8.0 (or lower) right now. That coupled with the fact that MA definitely diluted the crystals/sediment is telling me its not calcium phosphate. Thoughts?
Regardless, once i get the pool filter running again the spring I'll attempt to lower the phosphates using Orenda PR-10000 and attempt to vaccum out the precipitate.
Any other suggestions or immediate next steps?

 

[JamesW]

That coupled with the fact that MA definitely diluted the crystals/sediment is telling me its not calcium phosphate.

Acid will dissolve calcium phosphate.

 

[JamesW]

Calcium Phosphate

Calcium Phosphate | Ca3(PO4)2 or Ca3O8P2 | CID 24456 - structure, chemical names, physical and chemical properties, classification, patents, literature, biological activities, safety/hazards/toxicity information, supplier lists, and more.

pubchem.ncbi.nlm.nih.gov

Calcium Orthophosphates: Crystallization and Dissolution - PMC

pmc.ncbi.nlm.nih.gov

 

[cmdonnel]

Thanks James! Appreciate that update.
Is there anything I can do now to prevent this calcium from hardening onto the plaster? most of it still just seems like a white powder, with some of it actually forming into a crystaline particulate that breaks apart quite quickly when attempting to grab it.
I was going to wait to add the PR-10000 until the Spring because I want the filter to then pick up the resultant waste, but dont want this stuff to harden once the pool water warms up.

 

[JamesW]

Is there anything I can do now to prevent this calcium from hardening onto the plaster?

Brush as much as necessary to prevent scale.

Keep the pH from getting too high.