Trouble getting rid of organic stains

[ti_chris]

Hi,

Over the years, I've noticed my plaster pool getting larger and larger stains. I believe part of the issue is that I don't really do much during winter time. It's cold enough that algae don't tend to grow very quickly and I'm assuming that the lack of brushing once a week has made it such that the little bit of algae that was in there ended up staining the concrete. Regardless, I've tried to shock my pool and brushed the walls heavily but it's not going away. I've tried to drop some cal hypo at the bottom and leave it overnight and that actually helped to clean/bleach the stains that were below the granules (which is why I believe these stains are organic). The problem however is that there's some nasty stains on the walls and I can't exactly leave granules on the wall. Again, I've tried to scrub with a brush aggressively and I also tried to scrub the stains with a 3" puck but that didn't work. Interestingly enough, the stains tend to start about 1' from the waterline and they go all the way down until the floor shows up. The heaviest stains tend to be in the part of the pool that's shaded. What could I do to address the stains?

 

[Texas Splash]

I won der if some of those stains aren't part of calcium scale as well? Maybe organic mixed with scale? Do you have water test results you could share?

 

[ti_chris]

I won der if some of those stains aren't part of calcium scale as well? Maybe organic mixed with scale? Do you have water test results you could share?

I could totally believe that it's scale + algae mixed into it. At the beginning of the season, I emptied & refilled my pool because my calcium levels and CYA levels were too high. Right now all of my levels are perfectly fine. The scaling was harsh enough I ended up buying roughly 40 pumices and burning most of them on the tile lines. I also scratched some hard deposit on some of the plastic holes that my pool has to hold a pool line.

pH: 7.6
Chlorine: 4ppm
Calcium: ~340
CYA: ~40

Is there an easy way to tell & how would I go about addressing that (without something involved such as acid washing?). That said, I wonder why the bottom of the pool would be slightly different than the walls in this case?

 

[Texas Splash]

I can't confirm why the scale would be any different on one particular surface more than the other. We can call in a plaster expert if needed. But if you don't prefer to acid wash, you might call around to inquire about sand blasting. I've seen others take that route before.