Calcium chloride seems to have turned into white dust on the bottom, is this normal ?

[Stein]

First of all, thx a lot for this site, what I know about pool I have learned here !

When starting to turn my pool into shape and form and based on the guidelines here at TFP, among other problems I have had to raise the CH.

My values:

FCL 4,01
TCL 4,29
CC 0,28
PH 7,6
ALY 89
CH 243
CYA 36
Temp 91 F

Water appears crystal clear.

To get to this level of CH I have added 14 kg. (31 lbs) CH+ (Calcium chloride) during a 2 weeks period. It seems like after a couple of days suddenly the calcium ends up on the bottom like white/greyish powder that is rather hard getting loose, I need to help my robot manually scrubbing. My sandfilter is able to catch and hold most of it. I have also noticed that the steel latter has been covered and not shiny blank as before.
I am using bleach for sanitation and Calcium hypo for schock.

Any ideas on this will be highly appreciated.

 

[chem geek]

Welcome to TFP!

If the pH and/or TA were high when you added the calcium chloride, then it could have formed calcium carbonate, but your numbers look OK so maybe the product you used had something else in it other than calcium chloride. After you add any concentrated chemical, you should brush the area where you add it to ensure thorough mixing. Usually the calcium chloride will dissolve within 10 minutes or so. Also, if calcium carbonate is formed, the water would usually be a bit cloudy/hazy so it does sound to me like some other sort of precipitate formed or something that doesn't dissolve well was in the product you used.

It's possible that your reported numbers are wrong and the pH or TA are much higher than you think. The LaMotte Color Q can be a little flaky that way, though usually it's the CH where it tends to read too low when the CH is higher, but that's usually above 300 ppm and not at your reading.

 

[Stein]

Welcome to TFP!

If the pH and/or TA were high when you added the calcium chloride, then it could have formed calcium carbonate, but your numbers look OK so maybe the product you used had something else in it other than calcium chloride. After you add any concentrated chemical, you should brush the area where you add it to ensure thorough mixing. Usually the calcium chloride will dissolve within 10 minutes or so. Also, if calcium carbonate is formed, the water would usually be a bit cloudy/hazy so it does sound to me like some other sort of precipitate formed or something that doesn't dissolve well was in the product you used.

It's possible that your reported numbers are wrong and the pH or TA are much higher than you think. The LaMotte Color Q can be a little flaky that way, though usually it's the CH where it tends to read too low when the CH is higher, but that's usually above 300 ppm and not at your reading.

Chem geek, thx for trying to help.
I do see from my notes that I did put in baking soda the day after I added the calcium chloride the first time, also I see that second time I added CH+ it was 2 days after adding more baking soda. Is it possible that I have been to close in time with the chemicals ?

 

[TrevNJPool]

Are u dumping powder directly in the pool or diluting it with water?

 

[chem geek]

If your TA of 89 ppm was before you added baking soda, you should not have done that since there was no need to raise your TA higher if you are using a hypochlorite source of chlorine. You didn't say how much baking soda you added so I don't know how high your TA may have become. With circulation, you didn't add these chemicals too soon to each other, but you might have raised the TA and possibly the pH (some) from the baking soda and then the CH addition over-saturated the water at least locally causing calcium carbonate chunks.

As TrevNJPool asked, how did you add the chemical to the pool? Pre-mixed/diluted in water? Dumped in one place in the pool? Poured slowly over a return flow? The latter is what we usually recommend followed by brushing in the area where you add the chemical.

 

[Stein]

I am spreading the baking soda out on the surface with the pump stopped for at least 1 hour, and not more than 1 kg. pr. 24 hours. The CH I mixed in a bucket, stirring and spreading out on surface (pump running), adding more water in the bucket when the crystals were surfacing, stirring and spreading until all was in the water (according to the manufactures instruction). Afterwards everything seemed OK, no clouding and no visible stuff on the pool floor. But after a couple of days all the pool floor, latter and the pool lights had an evenly thin covering of dust, not like spots here and there. The CH is called CTX-22 (CH+) and states Calcium chloride 100 %. My PH was never higher than 7.7, but I see from my records that TA was at around 100 a couple of times during my period of problems.

So maybe that is the lesson I have learned, - keeping a lower TA ? Before I believed in the theory of TA 100-120, but I see that TFP has lower levels recommended.

As for the Color Q Pro, since we don’t have this professional pool stores here, I cannot say if it is accurate, but it seems to be at least consistent. When I add something the reading changes according to what should happen. The ALY readings can be a bit strange and I have a feeling that FCL > 3.5 sort of bleaches the reagent .. ?

Internet and nice people spending time helping others must be one the best things happened to mankind!

 

[chem geek]

So with the numbers in your initial post but using 7.7 pH, the Calcite Saturation Index (CSI) is +0.2 which normally would not be high enough for scaling. You are right that we normally recommend a lower TA when using hypochlorite sources of chlorine, mostly to reduce the rate of carbon dioxide outgassing that increases the pH and requires acid addition.

What is most odd is that there wasn't initial cloudiness. The local concentration of chemical when you add it would be the highest at that point in time.

By the way, we never recommend adding chemicals with the pump not running (except if one is using a flocculant, but we don't normally recommend using one, and even then one usually adds it with the pump running and then turns off the pump). However, your broadcasting the chemical around the pool should have prevented local clumping and again you didn't see any problem right away.

The pool behaved as if the CSI was OK upon addition but then the pH rose and precipitated calcium carbonate, but you say you didn't see a pH rise above 7.7 during this time. Very strange.

 

[Stein]

I have done some thinking. On the Cal Hypo box they say that the product should be added straight into the skimmer. Since this was before I found this site I followed the manufacturers instructions. With pump stopped added Cal Hypo into the skimmer, then starting the pump. Wow, - I could see like a like a grayish flood shooting out of the four return valves, and the water became unclear for an hour or two afterwards. I am thinking that although the PH in the pool was correct the PH in the sandfilter may have risen fast and high. Could this be the reason for the scaling ?

Never the less I had to call the experts as you can see :

 

[JasonLion]

Adding chemicals via the skimmer allows huge fluctuations of the levels inside the filter before the chemicals mix throughly throughout the pool. That could result in scaling inside the filter and right near the return jets, but would not be enough to cause scaling in the pool generally.

How are you testing your levels? I suspect that your CH level is higher than you think it is.

 

[duraleigh]

Your pump should be running ANYTIME you are adding chemistry.