first opening after new plaster - scale in Jacuzzi

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tolian21

Well-known member
Mar 27, 2019
59
NJ
Hi,

I had new plaster installed (polished stones capes, on the expensive side). Its very smooth. Maintained water chemistry perfect. Closed with CH around 310, TA 100, PH7.6, CYA 30. At opening CYA not registering, CH320-330, TA 100. PH was 7.6, I brought it down to 7.4.
Its a non-SWG pool. After opening, only jacuzzi section got a lot of calcium build up and rough like sand to the touch. Both sections are connected, so water always exchanged between the two. Pool is in perfect shape. How can one section of the pool get calcium deposits, maybe because Jacuzi has less water and more surface area?
Anyway, I drained the spa, and spent entire day polishing it with orbital sand paper and little acid washing in some parts. Looks like new and smooth now.

Questions:
1. Why did this happen in Jacuzzi only
2. How to prevent this in future, should I add some scale preventing chemical in jacuzzi for winter closing?
 
The LSI balance is the same as TFP CSI. I think Orenda is doing a bit of obfuscation between their crystals and scale to sell their product.

@onBalance @JoyfulNoise your thoughts on this?
 
Orenda is adding confusion to the mix and saying it’s actually from negative LSI during winter, not highly positive as with typical scale. my pool closing numbers are not too crazy. CSI does go negative with these numbers in cold temps, but nothing crazy. Maybe its attributed to pool still curing (done last may) and given that jacuzi has less water and more plaster surface it got over saturated?
it looked like sand Particles attached all over the plaster, can be removed with sand paper. a lot of work, but after I removed them, it does not look like plaster is damaged. So I am confused Why it happened and how to avoid it.
 
This particular issue is complicated and confusing. I will suggest that the crystals are not caused by aggressive water, and they are not caused by hard water and overly positive CSI (or LSI - same thing) water. OnBalance is currently researching and studying this issue. The initial results is indicating that too much calcium chloride (hardening accelerator) is added to the plaster mix. During the winter, the excess calcium chloride and calcium hydroxide (a by-product) dissolves (both compounds are soluble) out of the plaster and then forms (calcium carbonate) crystals on the surface due to the lack of water movement during the winter.

In this particular pool, it may be that the "jacuzzi (spa) material" (plaster) contained a high amount of calcium chloride, whereas the plaster in the main pool may have had a lower amount of calcium chloride added. And that would be why the difference between the spa and pool. This process may have run its' course and not happen again next winter. It appears to depend on how much of the hardening additive is added.
 
You could use Orenda's SC1000 when closing the pool. Try to delay the closing as long as possible and open the pool as soon as possible. Brush the plaster upon closing and opening. Maintain the water as you have been. There is a good chance the deposit won't happen again.
 
Wanted to follow up on my thread. 2nd opening, and same issue in attached jacuzzi. Opening measurements:
PH 8.0 (went up in winter, was 7.8 when cl
CH 380
TA 150 ( seems like it went up because I closed with 110)
CYA 30
Salt 2500

it looks like little sand particles on plaster that are easily bumped out by finger nail, will still require me some work to sand it off

Is it scaling from too much calcium or calcium crystals? I live in philadelphia area, so we see freezing in winter. Seems like with these numbers it should be ok at 40-50F.
The only difference is jacuzzi is shallow than pool, but its made from same plaster, had same water chemistry as pool at close
 
Why is the TA so high when you close the pool? What is the CSI of those numbers you posted?
 

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Do you keep your TA that high for a reason?

Odd that TA would increase over winter. Rain and snow does not contain carbonate alkalinity. So I wonder where it is coming from.
 
Last edited:
mknauss said:
Do you keep your TA that high for a reason?

When you get very cold pool water, it can scale much more easily. So lowering your TA prior to closing would prevent that.
Odd that TA would increase over winter. Rain and snow does not contain carbonate alkalinity. So I wonder where it is coming from.
Click to expand...

its a solid cover, so not much rain/snow gets there. I normally keep TA 70-90 during season, at close I bumped to 110 for colder temps.
Pool company that opened pool might have thrown some MPS shock at open, but I do not think it causes TA measurement interference, will find out what chemicals they added.
 
Picture attached. They look like salt sprinkles, and come off easily with a finger nail. I used pumice stone, and it came off easily and became smooth. I have nice 2 year old polished stones cape plaster.
I took off some of these crystals, and put muriatic acid on them, they dissolved. What do you think, is my LSI too negative or too positive in winter? It would seem it should be positive.
Why Jacuzzi only, makes no sense. the only difference its more shallow than pool.
 
For calcium scale to form, the CSI gets too positive.
You do not use dry acid do you?
The spa is a small volume, so something is getting in it over winter to change the chemistry.
 
mknauss said:
For calcium scale to form, the CSI gets too positive.
You do not use dry acid do you?
The spa is a small volume, so something is getting in it over winter to change the chemistry.
Click to expand...


I use only TFP stuff, HCL acid, baking soda, and liquid chlorine. I need to tell my pool company not to put algicide and whatever other winter chemicals they put at closing. Algicide would not cause it?

I was reading Calcium Crystals vs. Scale and they say you can get calcium crystals when CSI is negative also. They say water pulls calcium, and it can then precipitate as crystals.

Would scale look like salt crystals?
 
I question the statement in that article that calcium scale (crystals) can form at very negative LSI (the old index related to steam boilers).

I can imagine scale can form in many different patterns.

Algaecide should not cause the scale. Hopefully it is Polyquat.
 
Yeah, 2nd year this happened. You can see in picture crystals are clear like water.
What temperature should I put in CSI calculator to balance water for winter before closing ? Should I say put 45F? Is CH 380 OK for winter?
 
Does your water get ice on it? If so, more like near freezing would be appropriate.

CH of 380 should be fine.
 

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