Pool opening and robot filled with crytsal substance

oakridge

Silver Supporter
Jan 16, 2017
148
Outside Philadelphia
So for the second opening of our 2.5 year old pool, the dolphin cleaner pulled a ton of this bluish crystal substance. When it dries it became white. See attached pictures. Is this normal or an indicator that I need to do something to the water chemistry over winter or when closing/opening?

Thanks!

100855

100856
 

JamesW

TFP Expert
Mar 2, 2011
16,589
Likely to be calcium carbonate. Put a drop of acid on the stuff to see if it bubbles.

What were your chemistry readings on opening?

How old is the plaster?
 

oakridge

Silver Supporter
Jan 16, 2017
148
Outside Philadelphia
The plaster is 2.5 years old. Upon open pH was high, TA 100, CH 250, Chlorine basically 0. I left the pile outside so once it stops raining, I'll try the acid test. If it is calcium carbonate, what does that mean? I assume this amount is not normal. I'll also re-test the water after the rain lets up.
 
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Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
James will be back later I'm sure to follow-up. When you say the "pH was higher", what do you mean? Higher at opening but is lower now via acid? How high? If it's calcium (fizzes with acid), then we need to evaluate all test parameter results (not just pH) to see what scenario may have played-out in your pool. Hopefully it's nothing more that post-opening calcium that has disintegrated from equipment once you lowered your pH. But to make sure, please post all test items and include your water temp if possible. Thanks.
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
14,588
Bedford, TX
oak,

That is what happens to me if I let my CSI reading get away from me.. If I run my CSI between 0 and -.3 I don't have the problem..

Thanks,

Jim R.
 

JamesW

TFP Expert
Mar 2, 2011
16,589
If it's calcium, it could be from the plaster dissolving or from scale if the pH got super high. Let's see what the acid test shows.

Are you feeling the crystals attached to the walls, or anything in the pool?
 

oakridge

Silver Supporter
Jan 16, 2017
148
Outside Philadelphia
So the crystals bubbled when I applied acid. The pH was off the chart of the quick test when opened (only test I have is Taylor K-1000; deep purple/above 8). The pH now is around 7.5 after adding about 2 jugs of acid over the past four days). Chlorine is now around 4ppm. The rest of the readings are listed in my last post. I cannot yet do CYA as I am out of reagent. There are one or two white areas of (I suppose) calcium build up on the pool tile. The plaster does not feel rough, but it did upon opening last year. That went away as pH was stabilized and the cleaner ran a few times. My main concern is that this is Ca coming from the plaster due to elevated pH levels over the winter. Not sure I can do much about that as the lines were winterized so the acid would not circulate should I have added it. I have never calculated CSI/LSI and monitor it since the pool generally has been stable and problem free.

I am not sure if the crystals were there before or after opening. They were there after the first run of the cleaner (day after opening) and not visible in the cloudy, newly opened pool. So I am not clear how to determine if this disintegrated from the equipment upon opening. Water is clear now and nothing is coming up anymore. It was just the first few runs of the cleaner, just like last year. Sorry for the long post.
 
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JamesW

TFP Expert
Mar 2, 2011
16,589
It happens with any plaster but more with new plaster. To prevent, you would need to monitor and control the CSI. Periodically pull back the cover, test and add acid as needed. Brush the pool thoroughly to mix in the acid.
 

shoot_the_goalie

Active member
May 15, 2018
35
NY
I had this in my pool upon opening last year (tiny crystals all over the floor and walls , but only under the waterline; come off easily, but pain to clean up). It's probably calcium leeching from your plaster, probably due to too low calcium levels before closing, among other things. (What was your CH levels when you closed?). I have read recently that it's probably caused by a combination of 1) low CH levels, 2) high pH, and 3) cold water temps. Also, your current CH reading of 250 might be inflated, because you had this calcium from the plaster now in your water. Before I closed my pool this previous season, I set my CH level to 450 (also making sure my CSI was in good range). I just opened my pool a week ago (to a CH level of 275 - expected since I have a mesh cover), and no calcium crystals formed this year, so keeping the CH level high (in accordance with your CSI) at closing seemed to work.
 

shoot_the_goalie

Active member
May 15, 2018
35
NY
I'm definitely not an expert (so take what I say with a grain of salt), but after dealing with the problem a year ago, and it leaving a lot of people stumped, this is one of the articles I found that seemed to most likely explain the condition I was experiencing:

Calcium Scale ≠ Underwater Calcium Crystals

I'm still not 100% sure this is what I was experiencing last year, and regardless if Orenda has an agenda to sell products, but all I know is that when closing my pool, I made sure the CH level was high and that my CSI levels were appropriate. The problem did not return this spring.
 

JamesW

TFP Expert
Mar 2, 2011
16,589
In my opinion, that report is incorrect.

If acid makes it bubble, it's consistent with carbonate because carbonate releases carbon dioxide when acid is added whereas hydroxide does not.
 

oakridge

Silver Supporter
Jan 16, 2017
148
Outside Philadelphia
Thank you all for the thoughtful responses. I'll track CSI this season and do some research on potentially closing with a high CH level. My CH upon closing was similar to now and in range (260-ish). I used a solid cover.