I’m a rookie, recent pool owner. My plaster turns not white, but black(!) when vitamin c tablets touch light brown-tinted stains (about 2 inch circle). I hit the internet, and I now understand conceptually “dissolve the metallic solids with Ascorbic Acid, then keep them suspended with sequestrant.” I also think I understand that high pH is conducive to metals coming out of solution (staining) and very low pH is conducive to dissolving metals into solution from the copper heater elements.
Two questions: One, can I somehow “flock” or otherwise get the metal out (after Ascorbic Acid then sequestrant treatment in order to backwash out of the filter or direct to waste), even though it’s not algae and the water is already clear? (In other words, I’m looking for a long-term low-maintenance approach of metals/chemicals that I should aim at before just dumping chemicals in. I don’t simply want a precarious balance that works temporarily--but which needs a lot of time, attention and chemical$$, forever. Therefore I assume I need to get rid of metals, and not just keep them “sequestered” in the water.)
Two, what is the risk of treating as if there are metals in the water, and it turns out the tests are right, and there are none?--I’m not exactly thrilled with the idea of adding more of that (Ascorbic Acid) which turned my plaster black!
This staining is similar to others who have posted here (and I have learned a good deal from the following threads):
2008: “The vitamin c tablets started to roll to my deep end and along the way (you will not believe this) turning my pool [plaster] black again everywhere they ran (like fingers reaching out).”http://www.troublefreepool.com/black...elp-t8327.html
2011: “Found a brownish stain near the steps on the pool. Rubbed the [vitamin c] tablet onto it and the stain turned black.” http://www.troublefreepool.com/ascor...ck-t36452.html
2009: “The [vitamin c/ascorbic acid) tablets turned the plaster black in a 6 in circle on one of my steps… About 30 min later … was shocked at what the spot looked like. It was the whitest and cleanest 6 in circle in the whole pool…” http://www.troublefreepool.com/ascor...ins-t2298.html
For my own pool, after 30 minutes, and after 1 day and vigorous brushing, the black stains from vitamin c tablets were only a bit less intense—still a dark gray.
I had the water tested at pool store and the reading was zero copper. Other readings: Free Chl 2, Total Chl 2, pH 7.8, Total Alk 160ppm, CYA 0, Calc Hardness 250, Total Dislvd Solids 2800, no reading on phosphates or iron. I have 30K gal., sand filter, chlorine puck float. The pool is 30 years old and I’m suspecting 30 years of hidden metal build-up on the plaster, but little in current water. I’m even wondering if the original cement/plaster was mixed with high-metallic water, but the plaster doesn’t seem to turn dark where vitamin c only touches unstained areas—so I guess that tends to rule out metal inside the plaster as an issue. I just backwashed in case there were excess metals in the sand.
BTW, after my first chlorine shock, pool water turned from clear blue to clear green-blue (suggesting metals I assume); now it is back to clear blue. Right now, pool is not heated, about 65F, and under a type of pavilion (very low sun, low debris). I’ve been aerating with nozzles pointing up to help lower pH (to low 7’s, I hope) without chemicals.
Finally if Chem Geek or anyone could tell me why A.Acid would turn plaster or metals on plaster black, I’m very interested. Thanks for any responses—y’all have helped me already from other thread answers!
30K gal, plaster, sand, floating chlorinator