Light brown/tan stains in gunite pool

[adc]

I have brownish stains on the bottom and sides of my pool. I have tried shocking and scubbing but with no results. I did put some vitamin c in a stocking and put it on the stain in the shallow end with the pump off. After about 5 minutes it started to fizzle with a dark brown cloud around it. I removed the vitamin c and there was a dark colored stain where the vitamin c was. After about 35 miniutes the dark colored stain vanished, but it appears the original tan stain is still there.

Did I leave it on the stain long enough, I panicked when I saw the dark colored stain appear on my plaster. Please assist.

I have a swg, with well water. I did not know much about pool chemistry at first, so my ph and chlorine were high for the first couple of years. I now test my water at least twice a week, and the pool store says there is no metals in the water. I now use a metal trap to top off the water in the pool, and use Jack's Magic weekly.

Please assist. Thanks.

 

[frustratedpoolmom]

The pool store doesn't detect the metals in the water because the have deposited on the pool surface.

What you are describing sounds like it could be copper staining. If the AA treatment were to work - the vitamin C reaction would have been instant - not a darker stain after 5 minutes.

Did you regularly use algaecide as part of your pool care? Some algaecides are copper based, which could have resulted in your staining.

Unfortunately AA treatments don't work for Copper staining. Usually an acid wash is the last resort. How old is the pool surface? Acid washing shortens the life of the plaster so it's not something you want to do unless you have to. Can you live with the staining or is it very unattractive to you?

Do you go to the pool store for testing twice a week? Consider your own test kit, like the ones recommended here.
Test Kit Comparison

 

[frustratedpoolmom]

Here is something else you can try:
Fill an old, white cotton sock with dry acid and tie the top. Fill a small Tupperware container with stones or rocks (we want it to sink and not float) and cover, rubber band the sock to the underside of the container and place on stain (which is under water). Let sit 45 minutes but check at 15 minute intervals. If the stain lifts it probably is copper and the acid wash is just about all you can do at this point.

How long have the stains been present?

 

[adc]

Ok, I will try this. The stains have been showing for 3 years, they do not get any worst or better. It is starting to show more aroung the main drain. thanks