Just a little background. I made the dumb mistake of leaving 3" chlorine tabs on the bottom of the pool floor. The area around where the tabs were placed on the plaster surface got very rough. It is too cold to get into the pool and go under water looking but now I don't know what this is... The pool was green but is now otherwise stable.
What is this?
- Thread starter SpaceCoast
- Start date
Flying Tivo
TFP Guide
- Jan 24, 2017
- 2,969
- Pool Size
- 7500
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-40
Sorry to say but it appear that the Pucks acidity ate away your plaster. The darker areas are the gunite showing up.
- Jun 22, 2014
- 48,028
- Pool Size
- 17888
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
Hummm. Pucks are very acidic and shouldn't stay in one place like that. Although I do know that chlorine tabs can make copper staining worse. Do you happen to have a full set of water test results? can you tell us if any algaecides or pool store products have been used lately? Oh, and there is JamesW. 
It might be gunite if the plaster is worn completely away. It's hard to tell from pictures.
Try dropping ascorbic acid on the spots.
Try dropping ascorbic acid on the spots.
Im more concerned about the black spots than the (probably) yellow copper staining.
Do you think it is black mold or just the gunite and how would I be able to determine?
The gunite would be black, right?
If it is gunite showing, can I repair with some of that under water expoxy?
Do you think it is black mold or just the gunite and how would I be able to determine?
The gunite would be black, right?
If it is gunite showing, can I repair with some of that under water expoxy?
Also wondering if there is dirt stuck in the rough areas?
Basically, wondering if this is:
1. dirt
2. gunite
3. black algae
Basically, wondering if this is:
1. dirt
2. gunite
3. black algae
- Jun 22, 2014
- 48,028
- Pool Size
- 17888
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
1 - I doubt it. Too dark and should brush away.
2 - Possibly, depending on the age/condition of the plaster if the puck did any damage. Like James said, hard to tell from a photo though.
3 - BA can have that appearance, but it's odd (IMO) to be in such a circular pattern.
4 - Don't rule-out copper just yet. The acidity of trchlor/dichlor reacts with copper to make it turn black. That's why we asked those questions above.
5 - Try to show us some test results and chemical history to help give us a more complete picture of the water.
Copper can be black if it's in an advanced oxidation state from the chlorine.
Do your chlorine tabs contain copper?
Put vitamin C on a black spot to see what happens.
Do your chlorine tabs contain copper?
Put vitamin C on a black spot to see what happens.
It's unlikely to be black algae due to the high chlorine level near the tabs.
How old is the plaster?
How old is the plaster?
Sorry for the delay.
I left the tabs on the plaster over a year ago. The black stuff turned out to be dirt. I know because I got in the pool and it wasn't slimy and shooting it with a pressure washer quickly removed it. Unfortunately, the plaster in the area where the tabs were left is now rough. I have tried putting absorbic acid on the yellow stains, but nothing happens. I am considering to just sand it down?
I left the tabs on the plaster over a year ago. The black stuff turned out to be dirt. I know because I got in the pool and it wasn't slimy and shooting it with a pressure washer quickly removed it. Unfortunately, the plaster in the area where the tabs were left is now rough. I have tried putting absorbic acid on the yellow stains, but nothing happens. I am considering to just sand it down?
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