Calcium Crystals? or Scale?

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C

cmdonnel

Member
Aug 9, 2020
10
Fruitville, PA
Hi, I have a 4 year old Diamondbrite Quartz Plaster gunite pool that I was preparing to open for the season in the Northeast (PA). I dont have the exact numbers, but I know the water chemistry was good when I closed the pool last October. When I peeled back the solid cover yesterday however I noticed the entire pool (walls and floor) were covered in these calcium growths... crystals, or scale. I did alot of research on this forum and just wanted some help and confirmation on the path forward here.
Attached are a couple pics.
Once I fully open the pool later this week I will get exact water chemistry results, but the quick test I did last night revealed a high PH (8.5 or higher) and low calcium (around 100). Which makes me think the plaster was leaching calcium vs the water being oversaturated with calcium.
I had some diamond scrubbing pads and was able to scratch off the calcium in a couple test spots, but was hoping there was a chemical way to remove the calcium as well, or at least soften it up. I'm hoping it won't come to a drain and grinder. Do I have hope here.. balance the water, add a descaler, and brush and brush?
Thanks for any help in advance.

https://live.staticflickr.com/65535/53690352953_4fc5ec00af_n.jpg
https://live.staticflickr.com/65535/53690490154_f703d6bd37_n.jpg
https://live.staticflickr.com/65535/53690352958_ee86fe531b_n.jpg


Craig
 
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I think the article above is important. Looks to be calcium scale. Can you scrape some off and test with Muriatic Acid to see if it fizzes?
 
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I could be that CH is low because a lot of the calcium has fallen out as scale.

CH on its own is not telling us much, it's the combination of CH and TA (together CYA and pH which determine how much of the TA is carbonate ions) that determines how likely it is that calcium ions and carbonate ions form calcium carbonate that falls out of solution. Salt has an influence too as it shields those ions from each other.

We'll need a full set of water parameters, ideally also one from as close before closing as possible, to get a better understanding what's going on.

I'd recommend to start logging your test results in PoolMath, this allows much easier root cause analysis when things go wrong.

From what I can see in these pictures it looks like uniform scaling, not that easy to see from these angles and with the pool lights on.
 
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Thanks for the replies so far. Pool is being fully opened today and I'll post back with the full test results (from CLOSING last fall and today).
I did do the "fizz test" yesterday though and the scraping instantly fizzed and dissolved. So I guess that means they are Calcium carbonate.
 
Finally able to post some test results:

Last Fall when I closed my pool on October 24th, these were my test results (measured by the Taylor K-2006 and additional FAS-DPD kit):
ph: 7.6
Alkalinity: 90
Calcium Hardness: 300
FC: 12
CC: 0
CYA: 60
TDS (taken from the pool store measurement because I dont have a way to measure this): 3800 (note - this is a salt water pool)

Test Results from when I opened in the spring (5/2), with all the scale present:
ph: 8.5
Alkalinity: 80
Calcium Hardness: 200
FC: 0
CC: 0
CYA: 35
TDS (taken from the pool store measurement because I dont have a way to measure this): 3500 (note - this is a salt water pool)

What's interesting is when I put these numbers into the Orenda app to determine my LSI, the TDS value really throws off what I would expect. I was expecting the result to be scale forming (LSI > 0.3), but if I enter the TDS value of 3500, it actually says the LSI is "green".

From reading online and speaking to the great folks at orenda, I'm trying to lower the ph (and monitor or increase Calcium) and then also purge with their SC-1000 product. After adding acid and some liquid chlorine (amounts determined thru pool math), ph is slowly coming down and FC has gone up as expected. I'm ignoring TA right now to try to just get the ph down to 7.0-7.2 to see if it can help dissolve/soften the scale. Test results as of today (5/5):
ph: 7.5
Alkalinity: 60
Calcium Hardness: 200
FC: 7
CC: 0
CYA: 40
TDS (taken from the pool store measurement because I dont have a way to measure this): 3500 (note - this is a salt water pool)

Note - water temp is currently 65

Am I on the right track here?
Having gone through this, I see this is a somewhat "common" occurrence here in the NorthEast over the winter and plan to add some pumps and periodically check, circulate, and brush the water this winter to attempt to limit the ph swing.
As of right now, these calcium scale deposits cannot be brushed off (even with a wire brush), but can be sanded off using a diamond sanding sponge. I'm hoping a couple days of the low ph and the SC-1000 purge (to be performed on Tuesday) will help soften the scale.
Thoughts?
 
Unfortunately, I don't have a definitive answer for you on whether the problem is typical calcium scaling or what is known as calcium crystals (I posted an article on that topic). Both issues have a similar look.

With the pool plaster being four years old suggests that the problem is not calcium crystals. However, with the pH going above 8.5 and the calcium level decreasing indicates that it is more likely the "crystal" problem. What occurred with your pool was not caused by aggressive water. Has this pool been drained since new, or acid washed? Knowing this could shed some further light on this.

At this point, lowering the pH and TA and making the pool water aggressive (as you have been doing) and adding Orenda's product may help to remove the calcium carbonate deposit. But that program will need some extra time to react with the calcium carbonate. Leave the calcium level alone for now. Use a stainless steel brush that is more effective than a nylon brush. Sorry I don't have more answers for you.
 
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Really appreciate the responses. The pool was drained last year and the plaster was “polished” to remove an over exposed aggregate layer that was super rough. This was not scale but an actual plaster “defect” in workmanship. So maybe the new water and polishing the Plaster made it act like new again? Note- the polishing was done by draining the pool and using diamond buffing pads to go over the entire pool. That was done In april last year.. so you would think it had all season to cure. I did battle rising ph all summer , but I just attributed that to the swg and maintained it with acid weekly (it never got above 8.0)
 
Your additional information does shed more light on this issue, and you probably answered your own question.
Power polishing makes the plaster surface almost like new again.
One additional suggestion for the future is to try and brush the pool occasionally during the winter. That can make a difference and help prevent the crystals from sticking to the plaster surface.
And making the water aggressive this spring now will assist in slowly dissolving the crystals and making it easier to remove by brushing.

Here is an article that may provide some more info with your pool.

Why Are Calcium Crystals Forming in Pools?

In recent years, calcium crystals have been forming during the winter at a higher rate in some newly plastered swimming pools. From the reports we have heard, this problem seems to occur more often in the northeast of the country. Apparently, pool builders, plasterers, and service techs involved...
www.troublefreepool.com www.troublefreepool.com
 
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@onBalance , thanks again for your help and insight. I’ve been brushing and keeping the ph at 7.1 and TA around 45 and the scale is slowly coming off.
Question.. am I harming my equipment by keeping these ph and TA numbers? It’s only been this aggressive since Sunday but how long can I keep it this way without damage to heater, SWG, etc? A couple weeks?
 
Can you bypass your heater for a while to be on the safe side?

But as long as you keep your pH above 7, I don't expect problems. For the metal inside your heater and the SWG it is more pH that matters, not CSI. I reckon that your approach of keeping TA low and pH above 7 should work.

Just keep a good eye on pH and TA. If TA gets lower, the risk of pH crashing becomes real.

Let's see what onBalance thinks.
 
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