Probable Calcium Scaling


Jul 24, 2017
Cumming, GA
I have a gunite pool, ~16,000 gallons. The filter went out and it sat for around a year and a half. I know that's not good, I didn't have much choice in the matter... To make matters worse, I used flocculant incorrectly (through the filter) and ruined my sand. I replaced the sand and with the supervision of a professional emptied the pool, scooped all of the gunk and garbage off the bottom and immediately refilled it. I mainly did that because I couldn't see the bottom and I was afraid there still might be floc in the water which would ruin my new sand...

Anyways, I was able to get the water balanced (for the most part) and clear. Now my issue is the picture below. I originally thought it was organic staining (and part of it may be), but now I am pretty certain calcium scaling is playing a major role in the ugly look. I know for that year and a half the pH was sky high 8+ so I'm pretty certain it is calcium scaling with trapped dirt underneath. The discoloration is slightly abrasive to the touch. When I scrub it with a wire brush, a small cloud comes up but the marks are still there. My psi jumps fairly dramatically too. I know enough to be stupid about pool chemistry and I am quickly learning about CSI and it's role in scaling...

Here are my most recent results below:

FAC- 2ppm (CYA of 30 ppm I need this up to 5ppm)
TAC- 2ppm
CH- 250 ppm
CYA- 30 ppm (I'm keeping my eye on it)
TA- 100 pm
pH- 7.7 (trying to get it to 7.5)
TDS- 900

I'm pretty sure if I lower the pH to 7.2 and lower the alkalinity to 80 (and keep my eye on it daily), I can reverse the problem. In a perfect world (balanced 5 ppm FAC, pH 7.2, TA 80, and the rest of the numbers good) the CSI would be -.43. I'm assuming that with daily wire brush scrubbing might rectify the scaling? I'v heard of people rigging 80 grit sandpaper to their brush and lightly brushing? Pool.JPGI know there's a pumice type abrasive tool called a "stain eraser" that hooks up to my pole, I'm just worried its going to scratch the gunite (i'm probably being too chicken).

Scaletec makes a product for this exact thing, but if I'm learning anything it's that TPF does not advise anything beyond basic components for chemistry. Goodness knows I've burned myself a few times trying to take a shortcut.

I'm not sure if I'm on the right track or not, any advice would be really appreciated.


Gold Supporter
Jun 8, 2019
Milwaukee, WI
I’d start with the organic staining. If stuff is “proofing” up then you have dead algae. Your FC is very low. How are you getting your test results / what kit are you using for testing?