Over the past year or so I've noticed some brown stains appearing on my plaster. My plaster is ~3.5 years old and it was acid washed and re-plastered before I bought the house. I've tried putting pucks on the stains and they don't get lighter. I also tried some vit-C tabs on the stains and didn't notice anything either but the tabs were really small and hard to keep in place so I am not sure how good of a test that is.
Today I was adding acid to the pool (My PH always drifts up) and I decided to pour some muriatic acid right on the top stair where some of the stains were. It appeared to lighten them. Brushing the stains with a wire brush also has no effect.
The water has been tested for copper and iron I believe at the pool store and always come up as none - I haven't done one this year so I will bring a sample into the pool store and ask them to check again.
Any ideas? The pool was a mess for ~2 years before it was redone, could the stains be coming from below the new plaster? Going to try putting some vit-C tablets in an upside down glass or something to keep them in place and see if that has any effect. Its hard to get a picture of the stains as they show up best when the sun is going down but that makes getting a picture difficult as well.
My last test results were:
TA - 120
PH is usually between 7.4 and 7.8.. Was wondering if I should try lowing the PH really low and see if it lightens the stains? I've seem some people recommending absorbic acid but would muriatic work? I'll try to get the metals retested tomorrow at the pool store as my TF-100 kit obviously doesn't have those tests.