Good morning, coach. Glad to see you got a kit and glad your iron reading from pool store says .1 ppm, not higher, and doesn't show copper. The metals part is one thing pool store testing is useful for, though in your case there's much more concordance than usual with parts of the tests
To go back to your original concern about the stain:
I've got these dark shades in the bottom and dark spots forming. Pool was drained, pressure and acid washed about 10 days ago. Is this something to be concerned with?
Since the vit c test showed some improvement, there is reason to believe an ascorbic acid treatment would work. You can read up on the AA treatment to consider.
Ascorbic Treatment to rid Pool of metal stains
But again, since you just had an acid wash, we don't know age/condition of plaster, etc., I just want to be sure we don't misdiagnose a plaster problem for a coincidental metal problem, because its possible to have both. While ascorbic acid is gentler than an acid wash, its still acidic
Lets recap for the benefit of posters who might know more about plaster than I: correct anything I've gotten wrong here--
- Your ch does not seem high enough for scaling, but you just came out of an acid wash and refill
- The staining is getting worse, but did not appear until after the acid wash and after a high dose of algaecide
- You are not on well water
- the staining was also lightened after a errant puck sat on it for a long time
- pool store test reads .1 ppm iron, technically not enough to create a stain, unless all other iron has already precipitated to a stain
So, here are some questions that might help:
- On refill, did you also add a metal sequestrant or stain and scale product? If you have, the low reading likely suggests you need to top up...sequestered metal often won't read
- Why did you have the acid wash to begin with? We're there stains then that prompted same?
- Have you called the company that did the acid wash to see what they say about this new staining?
- What was the name of the triple dose of algaecide you used? Some of those contain copper. Even though you read zero on copper at the pool store, its possible it precipitated and caused the stain.
I will see if there's anyone about who can help determine what might be going on here.