Guys,

I am back to step 1, Stain is even worse than it was before. Floor and walls are covered with this brownish/yellowish layer. Looks very dirty. As soon as I drop vitamin C it disappears around the vitamin.

I went to the local pool store (Leslies) guys checked the water for metal and said 0 metal in the water. He couldn't even sell anything to me just said that my numbers are perfect.

Chlorine 4ppm
Total Chlorine 4ppm
PH 7.2
Alk 80-90
Cal 120-130
CYA 30

We had a heavy rain here and maybe that caused it to stain even more than it used to be.

I don't have anything in the pool that could cause it to stain. Pool heater is Aquacal h155 that has a titanium heat exchanger, filter Hayward DE EC-75 and polaris 380.

All pipes are PVC.