Slight yellow color on walls

[paul1971]

My pool pass the test but i do have a very very slight yellow stain on small section of the liner. I think is normal. And it brushes off

 

[reggiehammond]

Overnight Chlorine Loss Test to confirm if you have algae, SLAM Process to eliminate it.

If it's not algae, it could be iron staining precipitating from your water.

How do you chlorinate? How do you test your water? What is the source of your pool water?