Please help ID Pool stain

Dec 6, 2016
Hi. New pool owner since October. I been been trying to keep the pool balance using the BBB method since I got the pool drained back in November. The pool guy power washer it and he said he used acid with no luck. There are some dark stains all over the pool. It is worst around the deep end. I put a chlorine tab on a couple spots around the pool for about 5 minutes and it did not change. What should I try next?

Results from

FC: 2.5 (I added chlorine after this to bring it up to 5)
CC: 0
PH: 7.8
TA: 125
CH: 275
CYA: 40
Temp: 66



Mod Squad
LifeTime Supporter
Jul 10, 2012
Tallahassee, FL
Next if vitamin C! yep just some cheap vit. c crushed up in a sock and let it sit on one of the places or you can also rub the vit. c tablet on it.

Can you feel the stain if you rub your hand or fingernail over it?



TFP Expert
In The Industry
Jul 6, 2011
In these pics, is there water in the pool? Looks to me like typical wear on the finish probably from not being take care of. How old is it?
Dec 6, 2016
I will go get come vitamin c today thanks.
The pool is filled. House was built in 1996. The neighbor told me the pool was built later. I'm sure the pool was neglected for a while. When I google map my house, I can see the pool is filled up about 2' from the bottom and that's where most of the darker stains are.


Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
Aug 10, 2012
I agree that looks like worn out plaster. If it is smooth enough and doesn't leak then you can just live with it for a while until you are ready to replaster. But, it doesn't hurt to work on the stains, more here, Pool School - Pool Stains
Dec 6, 2016
I got some vitamin c today. Crushed it up and put it in a sock. I put it where it's the darkest near the drain about 8' deep and couldn't really tell any difference. But I also put some on a spot on the stairs and noticed a huge difference. So does that mean I can use absorbing acid to get rid of some of the stains? Where's the best place to get some?


TFP Expert
Mar 2, 2011
I think that the turquoise and black stains are likely to be copper. I suspect that there are also iron stains.