Stains on stone

[bbeckmann]

I noticed that a green stain has developed around the border of the pool. My wife tried to attack it with CLR, with no luck. In fact, there is a whitish residue on the stone that doesn't seem to come off that appeared after the CLR treatment. Chlorine levels did dip when we were out of town, but the water is crystal clear, and the chemistry comes up great.

Current numbers:
Chlorine: 3ppm
PH: 7.8
TA: 80
Calcium: 260
CYA: 50-60

Here's a pic of the stains. This was taken with a flash, which made the Green standout more and the white wash out a bit. It doesn't look nearly as bad! Green on the bottom, whitish above. Any ideas on how to get this stuff off?

 

[chem geek]

Unless you have a saltwater chlorine generator (SWG), according to the Chlorine / CYA Chart your minimum FC for a CYA of 50-60 ppm is 4-5 ppm FC so in case the CYA is 60 you should have 5 ppm FC as a minimum.

You can wipe the rock with chlorine that should kill the algae. You can still get some above the water line since water can evaporate and condense without the chlorine -- that's why skimmer baskets above the water line often have algae since the environment is moist -- this can be minimized by thoroughly cleaning the surface to minimize any stuck nutrients to the surface.

 

[bbeckmann]

Okay, thanks for the tip on the FC. I'll bump it up.

So, by wiping it with chlorine, does that mean just wipe it with some bleach?

Any thoughts on the white scaling on the stone and what might remove that?

 

[karmabiker]

White scaling looks like Calcium Carbonate. a 50/50 dilution of MA/water should make it fizzle green and dissolve. Wear appropriate safety equipment (goggles, mask, chemical proof rubber gloves) and please wait plenty of time and wash the rocks well between the CL application and the diluted MA application.

 

[chem geek]

Yes, just some bleach. As Chris noted, the white scale can be removed with dilute acid and you should make sure you thoroughly rinse between those cleaning steps because you don't want to mix acid with bleach -- that produces chlorine gas and other toxic gases.