Cobalt stains?

[Razorhog]

Each year I get some black marks on my fiberglass pool, which might be cobalt staining. CH is currently 60. Would raising CH help prevent these black spots and even remove the ones that are there already? Installed a SWG last week and FC is holding at 6 with a CYA level of 60. I will try to get pics.

 

[Razorhog]

It will take 26 lbs of Calcium Chloride to get to 220 ppm. Is that still the recommended level for fiberglass with SWG?

 

[mknauss]

I have no experience with low CH and cobalt stains. My fill water is 250 ppm CH so has never been a concern.

I think fiberglass still has cobalt so the recommendation stands. Though I do not think it needs to be that high. Lets ask @Texas Splash

 

[Razorhog]

Well walmart only had 5 lbs so that will get me to the 90's

 

[Razorhog]

@Texas Splash you have any thoughts on cobalt stains?

 

[Texas Splash]

Cobalt staining is one of those occurrences that we don't see all that often, and not the easiest to explain why it occurs. There was a very good discussion captured a while back with some of our heavy-hitters involved in the discussion. See this thread: Cobalt stains in fiberglass pools.

 

[Razorhog]

Ok well I'll try raising CH some. The black spots almost look like stars, hard to get a pic.

 

[Razorhog]

That pic is from the side wall, where I see them each year. Have some on the bottom too. It has to be something with how the fiberglass shell is produced. All in all they aren't too bad, it's just that the water is so clear you can see them

 

[Texas Splash]

I suppose this pool no longer has a warranty? Ever asked the manufacture? Have you ever tried some 600 grit wet/dry paper to one of the spots? There's a morbid curiosity in me to see if they go away with sanding or if it brings them more to the surface.

@JamesW, you ever see this?

 

[JamesW]

Possibly cobalt stains.

Black mystery stains

I have 2 large and several small ones. The large ones are quarter sized. I must have some small chips in the gelcoat where it starts because it's always the same places. They flare out with water flow. I can spot treat with citric acid and they fade or go away but come back in a month. Water is...

www.troublefreepool.com

 

[Razorhog]

I suppose this pool no longer has a warranty? Ever asked the manufacture? Have you ever tried some 600 grit wet/dry paper to one of the spots? There's a morbid curiosity in me to see if they go away with sanding or if it brings them more to the surface.

@JamesW, you ever see this?

No, I’m second owner and believe the pool is 12 years old. Not sure about sandpaper but now I’m curious too...