first opening after new plaster - scale in Jacuzzi

[tolian21]

I've been reading articles from Orenda, and becoming more convinced that my water was suffering negative LSI. My PH was actually higher at open, 8.0. I closed at 7.7-7.8, PH.

Its interesting that Orenda recommends raising calcium 500-550pm

"Do not be afraid to raise your calcium to something way higher than you would operate in the summer. 500 - 550 ppm+ is great! If your pool freezes, 400 ppm calcium hardness is the bare minimum in our opinion. Keep in mind, rain and snow will get into your pool (unless you have a solid cover), and this precipitation will dilute your water."

 

[tolian21]

Getting in touch with Orenda and sending crystals for analysis. Its likely due to negative LSI from what it looks, the analysis will confirm.

 

[mknauss]

Let us know. Makes no sense to create scale with low CSI -- again -- LSI does not work well for pools. It is for steam boilers.

 

[onBalance]

Tolian21, do the salt crystals rapidly fizz a lot, or just a little, when acid is added?

 

[tolian21]

Let us know. Makes no sense to create scale with low CSI -- again -- LSI does not work well for pools. It is for steam boilers.

Will do, the theory that water became not balanced (corrosive) due to negative LSI//CSI when it become very cold. It sucks out calcium from plaster, but when temperatures raise and LSI is no longer negative, the calcium excess precipitates out of water as calcium crystals that are deposited on plaster.

I plugged in my numbers at pool closing into CSI calculator
PH 7.8
CYA 30
Salt 3200
CH 380
TA 110
Temp 35F
------
CSI: -0.15


I know its not negative enough, but perhaps it was negative enough to pull some calcium from plaster. I removed crystals, and overall plaster in good shape, I do not see a lot of etching, though I think there is some of it that did not exist before.

I will follow up once I get results from Orenda and will share their recommendations.
One thing about liquid chlorine, while its great for not increasing CYA, it does add salt which needs to be accounted for as it makes water more corrosive.

 

[onBalance]

It is a mistake to only try and find a water chemistry balance reason for this to happen. This issue is probably not about the balance of the water, and whether it is LSI/CSI aggressive or scale forming. It is likely about the fact that when plasterers add a lot of calcium chloride to a plaster/cement mix, that alone causes calcium (in the plaster) to naturally bleed out overtime. Again, that will happen whether the water is aggressive or balanced, no matter what. When calcium naturally bleeds out, it can become scale on the plaster surface when the pool water is balanced, not when it the CSI/LSI is aggressive.

Tolian21 and Marty, you are correct that a slight negative CSI will not effectively etch a plaster surface, nor create calcium scale.

It would be interesting if you could possibly provide a short video on adding acid to the calcium crystals to view the results.

 

[tolian21]

Plaster was placed 3 years ago and this is a second opening with a new plaster and both times during open I found these crystals in the jacuzzi only. Maybe because jacuzzi is shallow it experiences more drastic temperature fluctuations in winter than pool? Its weird that with old plaster I never had this happen, and I did use similar water chemistry.
If its something specific to plaster (same as pool), 3 years after plastering seems like a long time to have calcium leak?
here are the crystals scraped. Will try to make video dissolving it

 

[onBalance]

The spa could contain a very different "batch-mix" of plaster than in the main pool, and often does. Some plasterers are in a hurry and want the spa plaster to harden rapidly, and hence, add more calcium chloride.

Your pool is not the only case of this type of problem. There have been similar "scaling" cases found in the main pool and not necessarily in spas throughout the Northeast. IMO, that suggests something other than water temp variances. And I don't see how there could be significant temps differences from pool to spa.

Lastly, you have mentioned that the water chemistry of the pool and spa were similar prior to winterizing. If so, wouldn't that suggest something else is the problem?

 

[ajw22]

To contribute to this discussion, yesterday my pool and spa was opened with 47 degree water temperature. The pool water was clear but the spa had a layer of "white stuff' floating in the water on the bottom and on the benches. The spa is drained at closing but always gets a pool of water in over the winter. In 16 years opening this pool I have never had a layer of white stuff like this in the spa.

The pool water pH was very high So far I have added 3 gallons of 31% MA and may have the pH to 8. I am still working on that. No, I have not checked TA yet.

Back to the spa, Most of the white stuff dissolved in the water when the spa was filled and flowed into the pool. There were some places on the floor and bench that had a white coating. I brushed those areas with my wire brush and got some but not all out.

So I decided to give the spa a bit of an acid bath and poured some MA in and brushed it around. The spa is not running and the spillover not running. The pH test was yellow however low that is. Brushing the white areas looks like it has removed them. I am letting the spa soak in the vinegar solution for a few hours then will run the spillover and dump the spa water into the pool.

Oh, and before I began all this pH tinkering I closed my heater bypass and took it out of the water loop.

So something strange happened with our weather in the Northeast this year. I never opened to such low pH or this white stuff in my spa.

Just letting @tolian21 know he is not alone in NJ.

 

[tolian21]

Lastly, you have mentioned that the water chemistry of the pool and spa were similar prior to winterizing. If so, wouldn't that suggest something else is the problem?

Maybe because SPA is shallow, it has higher ratio of plaster surface area to water ? Its possible they used something different for SPA to apply plaster, but 3 years later having problem? Perhaps bad workmanship.

 

[tolian21]

Just letting @tolian21 know he is not alone in NJ.

Thanks, the winter is in NJ is crazy, its either cold or warm.

 

[tolian21]

BTW, over winter my TA increased from 110 to 150 (and thats in entire pool after running pump). Orenda mentioned that it could make sense if water become very aggressive
"alkalinity climbed due to new hydroxides introduced to your water (calcium hydroxide). It carbonated slowly into crystals as it etched out of the surface."

Getting crystals shipped, will be interesting what they find.

 

[onBalance]

Aggressive water does not cause calcium carbonate crystals to form.

What can cause calcium crystals to form is for the plaster to naturally bleed out (or release) calcium (because it contains excess and soluble calcium hydroxide and calcium chloride) making the pool water "scale forming" and that can result in calcium crystals forming.

Also, a defective (micro-cracking), deteriorating, and porous plaster surface can break down and naturally and easily release soluble calcium hydroxide from the plaster matrix and increase the calcium and/or alkalinity content of the pool water.

Note: Many in the pool industry don't realize that calcium hydroxide is somewhat soluble and does not need aggressive water to dissolve away from the plaster surface. Again, calcium hydroxide can be dissolved by perfectly CSI balanced water.

 

[tolian21]

Aggressive water does not cause calcium carbonate crystals to form.

Interesting, its different view point from Orenda.
Since its 2nd opening with new plaster and it still happened, can plaster still be finishing "curing", or would be a defect at this point? The plaster appears to be in good shape.

Orenda is recommending for anyone who lives in freezing temps to bring CH 450-500, and balance the water at 32F for winter.

 

[onBalance]

It requires SEM analysis to see some defective issues of underlying plaster problems.
Orenda's recommendation to raise the CH levels does happen to help with this situation, but that does mean or prove that the problem was caused by aggressive water. Raising the alkalinity to 200+ ppm instead would also help.
I think it is somewhat fortunate that only the spa has the problem. Much easier to drain and remove the crystals.

 

[trivetman]

Jumping onto this thread as I opened with crystals that look identical to Tolians this year and am in the same NE area. I also had plaster redone not long ago. Basic white plaster refinished in 2019 and then the steps only redone in Sept 2020 as the redo was cracking and delaminating. I did not get crystals opening in 2020.

Whatsthis??

A ton of these ‘crystals’ are in the pool getting cleaned up by the robot after taking the tarp up and opening up? Any ideas what it might be. Pics are a ‘wet’ and a ‘dry’ look. It doesn’t seem like its the plaster deteriorating. Ive had that happen on old plaster and that was more like a...

www.troublefreepool.com

 

[tolian21]

Jumping onto this thread as I opened with crystals that look identical to Tolians this year and am in the same NE area. I also had plaster redone not long ago. Basic white plaster refinished in 2019 and then the steps only redone in Sept 2020 as the redo was cracking and delaminating. I did not get crystals opening in 2020.

Whatsthis??

A ton of these ‘crystals’ are in the pool getting cleaned up by the robot after taking the tarp up and opening up? Any ideas what it might be. Pics are a ‘wet’ and a ‘dry’ look. It doesn’t seem like its the plaster deteriorating. Ive had that happen on old plaster and that was more like a...

www.troublefreepool.com

Do you have numbers before close and right after open?
Did you experience alkalinity increase as well?

 

[trivetman]

After
Cya < 30
Ch 320
Fc 1.5
Ph high well over 8.0
Ta 70
Water Temp cold. Under 60 d.f.

Before
Cya 40
Ch 300
Ph 7.4
Ta 40

So yes TA went up but not a ton.
CH I consider the same as 20 is within testing error (also I get some wierd metals interference with my ch test so have to dilute and double the results). Surprised CH didn’t drop as it seems to be precipitating out of the water.

 

[trivetman]

Does new plaster drive TA up? Clearly it does the ph for some time and the two measures are linked.

i had steps replastered last Sept and had attributed the TA and PH spikes on opening at least in part to that. We also got a ton of snow over the winter and my cover is mesh so that all went in the pool.

 

[tolian21]

In

Does new plaster drive TA up? Clearly it does the ph for some time and the two measures are linked.

i had steps replastered last Sept and had attributed the TA and PH spikes on opening at least in part to that. We also got a ton of snow over the winter and my cover is mesh so that all went in the pool.

I was told, When water becomes aggressive it dissolves plaster and produces calcium hydroxide which drives TA up. I think this can happen when plaster is less than 1 year old, but mine is 2 years old, so I would think it should not be the case. You closed with very low TA.