Black stains just keep getting worse

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
32,956
Laughlin, NV
Preferably just the SWCG. Does your SWCG have a timer it operates through? How do you ensure the SWCG does not have power to it when the pump is not running?
 

onBalance

TFP Expert
LifeTime Supporter
In The Industry
Jul 25, 2011
1,041
Utah
Rich,
How old is the plaster finish?
When did the dark stain first appear?
Are there other dark discolorations in other parts of the pool?
 

Rich G

Well-known member
Apr 7, 2018
61
WPB, FL
Rich,
How old is the plaster finish?
When did the dark stain first appear?
Are there other dark discolorations in other parts of the pool?
Almost three years
First one appeared maybe a year ago and I didn’t think much of it
Discoloration is only one the sunshelf and exit step which both don’t get touched by the auto vacuum... the horizontal and floor surfaces are fine
 

onBalance

TFP Expert
LifeTime Supporter
In The Industry
Jul 25, 2011
1,041
Utah
Copper staining should not be ruled out. The water needs to be tested for copper content. It also might be plaster discoloration, but it is hard to tell from the photo. I doubt it is algae.
 

Rich G

Well-known member
Apr 7, 2018
61
WPB, FL
Okay update after the overnight FC loss test

02/09/20 7:45 PM
FC 9.2
CC 0.2 (maybe)
PH 7.6

02/10/20 6:45am
FC 9.4
CC 0.2 (maybe)
PH 7.6

I realize there is probably some error in my measurements depending on how clear is clear when checking the FC, each time it could have used maybe one more drop but it was so close I stopped. Either way I would say I passed the overnight FC loss test.


That said, it looks like I need to get some vitamin C tablets and dry acid and do those tests next.


On a side note, on my Facebook page all the pool people are saying phosphates but from what I am reading on this forum and other places that is not the case. On top of that doesn’t phosphates just encourage algae growth so I should have failed my overnight FC test if phosphates were the issue?


Thanks again for all the help
 

JamesW

TFP Expert
Mar 2, 2011
20,676
It's not phosphates. I don't think that it's copper. It might be silver. Have you ever added silver based algaecide?
 

Rich G

Well-known member
Apr 7, 2018
61
WPB, FL
It's not phosphates. I don't think that it's copper. It might be silver. Have you ever added silver based algaecide?
Only stuff I have ever added
Stabilizer - Amazon.com: Clorox Pool&Spa Chlorine Stabilizer 4 lb: Industrial & Scientific

Calcium - Amazon.com : Pool Mate 1-2825 Calcium Increaser for Swimming Pools, 25-Pound : Garden & Outdoor

Calcium - Amazon.com : Clorox Pool&Spa Calcium Hardness Increaser 5 lb : Garden & Outdoor

There were some granules that the pool store gave me, I wish I kept the bottle but it smelled like pure chlorine granules

The only other stuff I have added has been muriatic acid and salt
 

Rich G

Well-known member
Apr 7, 2018
61
WPB, FL
Bad news..
I put vitamin c tablets in a sock, dry acid in a sock and scrubbed with a chlorine tablet and none of them even phased the stain...

I’m almost wondering if it would make sense to just drain some water out and pressure wash the stains
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
I’m almost wondering if it would make sense to just drain some water out and pressure wash the stains
If the stains are isolated to the steps, you may be able to do that. But it would ideal to know why/how they got there to start with to prevent recurrence. If we rule out iron, dry acid would indicate copper (although doubtful, you never know), last would be organic (algae) ingrained stains. You could lay a tab/puck on the stain for about 5 min if not tried already. I couldn't recall.
 

Rich G

Well-known member
Apr 7, 2018
61
WPB, FL
If the stains are isolated to the steps, you may be able to do that. But it would ideal to know why/how they got there to start with to prevent recurrence. If we rule out iron, dry acid would indicate copper (although doubtful, you never know), last would be organic (algae) ingrained stains. You could lay a tab/puck on the stain for about 5 min if not tried already. I couldn't recall.
forgot to mention I let the puck sit on the stain just like the dry acid and vitamin c before scrubbing... the pool store folks think it’s black algae which is why the black algae remover got rid of the stain last time and that my phosphates are too high which is why it came back...
gonna take a sample to them to test on Saturday
 
Last edited:

JJ_Tex

Bronze Supporter
Jul 17, 2019
1,623
Prosper, TX (DFW)
Have you read the article on Black algae?

Note the way to test is to scrape off some and smear it on a piece of paper, or something else white. If it is a greenish color, then it is black algae.

 

Rich G

Well-known member
Apr 7, 2018
61
WPB, FL
Have you read the article on Black algae?

Note the way to test is to scrape off some and smear it on a piece of paper, or something else white. If it is a greenish color, then it is black algae.

Yes, and I can’t scrape any of it off...

I took an underwater video of the stain

 

JJ_Tex

Bronze Supporter
Jul 17, 2019
1,623
Prosper, TX (DFW)
Pool store gave me some granules you sprinkle on them and let it sit overnight with the pump off and it went away but a couple weeks later it came back.
I re-read your entire post, and your very first post caught my eye. So you sprinkled something on the spots from the pool store, and they went away for a few weeks. Do you know what this "something" was?

Clearly that pool store stuff isnt a long term solution, but the stain reacted to it. Find out whatever the pool store stuff is, and it will help the experts here identify the true problem and help you fix it.
 

Rich G

Well-known member
Apr 7, 2018
61
WPB, FL
I re-read your entire post, and your very first post caught my eye. So you sprinkled something on the spots from the pool store, and they went away for a few weeks. Do you know what this "something" was?

Clearly that pool store stuff isnt a long term solution, but the stain reacted to it. Find out whatever the pool store stuff is, and it will help the experts here identify the true problem and help you fix it.
I plan on stopping in Saturday to see if they still have it.. I will report back