Stain again too.

[ambereze]

I have drained my pool (this past weekend) and gotten the cya down. Two days later the stain is coming back . I have a fiberglass pool 8100gal with chlorine depenser. TA 171. PH-7.7 , Calcium Hardness 156, CYA 26 , We have always used well water, and when we refilled we put in county water , ouch. Thinking it was the well water, now it's back........Please help, I have been working on this for 6 weeks.

[Backglass]

When you drained some of the water, you also drained some of the metal-removing products you may have added in the past. Add some more sequestrant. If it doesn't help you may have to to the ascorbic acid treatment.