After taking the water out of my pool to do an acid wash the pool person suggested that because the walls where discolored a tan shade he would ruin the plaster if he used enough muriatic acid to remove the discoloration.
We tested an area inside the spa wall and even with 75% sol'n of muriatic acid the tan discoloration remained. He left. Reading about doing the chewable Vit C test on TFP, I did the test on a small section of my pool steps. Remember no water in the pool. The tan came out and the plaster was a nice white shade, in fact brilliant.
So I decided to refill the pool (20k Gal) and do the ascorbic acid treatment. Initially added 1lb of citric acid and 2.5 lbs of AA...was sold the wrong chemical at the pool supply store, that is why the initial dose was citric acid. Again reading lots on this subject on TFP, I believe that the blended two was not a problem.
Probably my 1st mistake. The water reacted and became milky white....the ca plus what I think is ferrous ions precipitated out. Talked with a manufacturer of stain out and he suggested using his product which contained EDTA...Added 32 oz, but the precipitate remained...added another 32 oz and still no results. This is happening over 2-3 weeks. Then added 32 oz of oxalic acid.
Did not do my homework...stupid idea. Also, I cleaned my filter 3 times and backwashed numerous times.. The milky white became a little less, but still can't see thur to the bottom of my 9ft deep end. When cleaning and catching the grey/white caulky substance from my filters I thought I was making progress.
Since putting fresh water in the pool my Cl and CYA were zero. My Ca was 150....TA 100.....Ph 7.2. After adding the above chemicals the Ph dropped to 6.8...only change.
Lastly I put 1.5 ilbs of Alum to floc the water, some floc appeared but not enough to clear the water. Lastly, removed all the water from my spa, refilled with fresh and the milky white reappeared. I seems the ca carbonate or ca Oxlate with fe is attached to the pool walls...the discolration did not appear after I put water in the spa..
Even if I dump all 20k gals of water, I believe the issue will remain...until I get the precipitate off the pool walls....especially the Fe.
Anyone who has recently had success with AA and precipitates pls help!