What is going on with this stain?

[ChrisL75]

So I have a couple of dark spots on the bottom of my pool. I placed some ascorbic acid on one to test it. Seemed like it made the stain spread with a brownish color. I travel for work so didn’t have anymore time to mess with it. A couple months go by and I now have what is going on in the photo. The one stain is kind of like my control, I didn’t mess with it. The other looks like I ****** it off terribly and has grown into a huge mess.

I’m about to travel home finally and hope to have about two weeks to fix this. Your help is appreciated. I have seen the guide on stain removal. I was just expecting the ascorbic acid to lift the stain not turn it into some kind of monster.

 

[Texas Splash]

Do you have any dry acid you could try on the stains? I would try that since the Vitamin C made it worse. See what kind of reaction you get. It would also be helpful to see a full set of test results next time you post just so we can be assured of what those levels are like. Other than salt for your SWG and muriatic acid, have any other products been used in the water that you know of?

 

[ajw22]

Looks like a rebar rust stain bleeding through the plaster. See if a magnetic will stick to the spots. Localized acid poured through a funnel can remove it but it will return. Fix is to cut out the rusting rebar that is too close to the surface and replaster.

 

[ChrisL75]

How do I share my logs on pool math?
The three things I have added to my pool since I have owned it was salt, muriatic acid, and dry stabilizer. Oh and some liquid bleach. Chemistry was way out of whack when I got the pool so did a water exchange in the beginning. City water.

I took a close look at the stain with a mask on and it just looked black and on the surface. Didn’t turn brown and nasty like this until I gave it some vitamin c. Don’t have any other acid at the moment but I can get some to try if I know what to get.

 

[ChrisL75]

Fc 18
Ph 8.2
TA 90
CH 400
CYA 60
Salt 3200
Temp 73*

chlorine creeped up while my wife was visiting me in Texas where I’m working. She has turned off the chlorine for now.

 

[Texas Splash]

I see your Poolmath logs now. I would lower the pH for sure. Get it down to about 7.6 or so. FC is a bit elevated for a salt pool. Did you just complete a SLAM?

 

[Texas Splash]

When you can get your hands on some dry acid, try that as well. The fact that the Vitamin C made the stains worse has me thinking it's copper. You can put the dry acid in a sock and tie it to the end of a pole to hold it against the stain if that works better for you.

 

[ChrisL75]

I’m guess the chlorine went high while the wife was gone due to winter approaching. Ph creeps up every week and we add acid to bring it back down. She just hasn’t added it yet.

one other idea is the previous owner said her kid and his friends would throw change in the pool and go dive for it. You think a couple of pennies laying on the bottom for a long time can cause some staining? I’m just really hoping it’s not the rebar idea mentioned above.

 

[ChrisL75]

What dry acid are you suggesting and where do I get some? Never used any before. Thanks for your help.

 

[Texas Splash]

The coin game might be related. If the copper residue remained and the plaster was never acid washed, it may be embedded in there. You'll know for sure once you do the test, but that's very possible. Also keep in mind that an elevated FC and pH will aggerate metal staining. So once the FC drops back down and you get the pH under control, the staining may subside a bit - maybe.

 

[Texas Splash]

Dry acid is sold by pool stores and the pool departments of some big box stores. Dry acid is sold under various names, including PH Down, PH Reducer, PH Decreaser, Lo-n-Slo, etc.

 

[JamesW]

It's probably rebar.

See if a strong magnet will stick to the spots.

 

[JamesW]

Black spot on Diamond Brite pool surface

I have a black stain on the wall of my pool, it is ~ 1.5' below the water line. I have showed it to the people at the local pool store and they had me treat it for black algae, but it did not take care of the issue. Please see attached pictures, can anyone ID that spot, if so would you know how...

www.troublefreepool.com

 

[ChrisL75]

It's probably rebar.

See if a strong magnet will stick to the spots.

Yeah I plan on that once I get home in a week or two. Thanks.

 

[Lilypad]

Before you add any acid to adjust pH —- Retest your pH after your chlorine drops below 10. You will get a false pH reading when FC is higher than 10.

 

[Texas Splash]

Before you add any acid —- Retest your pH after your chlorine drops below 10. You will get a false pH reading when FC is higher than 10.

Good point.