Stain help

[mrhappye]

I have a plaster pool and SWG.
There is a tan stain on the plaster which is worst around the main drain in the deep end. I dropped some ascorbic acid tablets on the stain and it turned black. I brought the water to Leslies and it tested negative for iron and copper. I don't want to purchase any stain removers until I know what I am dealing with. Any ideas?

FC 4
TC 4
Salt 3100
CH 200
CYA 60
TA 120
pH 7.8

 

[zea3]

Not sure what it is, maybe tannin stains? Did you have a lot of leaves lay in the bottom of the pool for a long time? Try dropping a trichlor tablet on the stain and see if it makes a difference.

 

[mrhappye]

Not sure what it is, maybe tannin stains? Did you have a lot of leaves lay in the bottom of the pool for a long time? Try dropping a trichlor tablet on the stain and see if it makes a difference.

I have dropped some granular chlorine on the stain but nothing happened.