Please Help! Dark “Bathtub” Ring

[TheIdiotDad]

Long story, but I’m certain this stain was caused by ascorbic acid powder. Maybe it pulled out some copper?

I have tried acid 50/50 dilution, pressure washing, sanding…can’t get it to go away. It looks way worse when wet.

Any ideas? I’m just sick about this!


I have the same issue in my hot tub.

Thanks for your help!

 

[ajw22]

How old is your plaster?

Can you post some wider shots of what area in the pool we are looking at?

How long has water been out of the pool?

 

[TheIdiotDad]

Plaster is 11 years old. Water has been out of the pool for two weeks.

 

[ajw22]

It looks like some type of acid pooled in the deep end of the pool and etched the plaster.

Only a new plaster job will fix it.