Low Calcium and Calcium Scale

[Andrewp]

The Taylor calcium drop test shows a level of 120ppm in my saltwater pool, but I seem to have scaling on my marble tiles. I scraped some off and put it in HCl, where it fizzled, which I am assuming means it is calcium. Would it be possible to have calcium scale with a ppm of 120 or could it be degradation of the tiles because of low calcium? My Dolphin vacuum picks up a lot of white sediment.
Here are the other results:
Ph- 7.8
Alkalinity- 60
Calcium- 120
CYA- 40
Salt- 3600
Free Cl- 3.5
Combine Cl- .25
Temp- 33°c
CSI- -0.38

 

[ajw22]

Show us a picture of the calcium scale you are discussing.

Waterline scale comes from the evaporation of pool water leaving the calcium on the surface. It can develop with any CH level.

 

[Andrewp]

So it is possible that I need to add CaCl2 as Pool Math suggests, even though I have calcium scale? Which, btw, occurs everywhere under the water, not just the waterline.waterline.

 

[ajw22]

So it is possible that I need to add CaCl2 as Pool Math suggests, even though I have calcium scale?

Yup, you need at least 200-250 ppm of CH to protect your plaster.

Calcium Hardness - Further Reading

www.troublefreepool.com

Which, btw, occurs everywhere under the water, not just the waterline.

That looks like a mixture of Efflorescence - Further Reading coming through your grout lines and Waterline Scale Removal - Further Reading

 

[ajw22]

The white line at the tiles isn’t so much “scale” from a chemical imbalance but more a consequence of evaporation and precipitation. As water evaporates at the interface of the tile and waterline, some dissolved solids, like calcium, salt, silicates, etc, will precipitate out of solution. That scale gets deposited on the tiles. Nothing will stop that because concentration changes, not chemical ones, drive the process. This is why spillover spa faces will always develop a white crust of evaporite.

The best you can do is always try to maintain a low saturation index to promote dissolved solids staying in the solution and then scrubbing the tile line regularly. Tile cleaners can help keep tiles clean, but they require regular application and lots of elbow grease.

 

[Andrewp]

I have already added about 20kg of CaCl2, and I will add more to get it to 200. I don’t think it can be efflorescence because the pool is not in the ground, it is raised to be level with the house, which is on a slope. There is a clear difference between the tiles above the waterline, which are still shiny and smooth. The tiles below the waterline are rough, like something has been added or taken away, but I’m not sure which. A steel brush does not remove anything, a scraper does. However, I can’t tell if it’s removing something that was added or just further degrading an already degraded tile. From my reading, that is what a lack of calcium will do, degrade the tile, correct?
Plus, it has been a struggle to keep the pH in range, it is always high and I have to add a few ounces of HCl every few days. Could that have something to do with the long drop to the gutter?

 

[mknauss]

Can you add your test kit brand and model to your signature?