Brown spots on blue sapphire granite coping....any idea how to get rid of them?

[three4rd]

Hi,

I'm disappointed that after only a year my new granite coping and caulk is developing what looks like rust-colored stains. Any idea what it might be? An increasing number of stones seems to be affected. There are no overhanging trees so I don't think it would be some sort of sap. Lately I have been using acid magic to get rid of calcium deposits on the tile and grout, so would it be ok to try a diluted acid magic solution on the coping? I tried to upload a picture of it but it didn't work.

Thanks for any suggestions.

Keith

 

[YippeeSkippy]

Did you use well water to fill the pool with? Does it have a lot of iron in it?

 

[JamesW]

Try ascorbic acid (vitamin C) on a spot to see what happens.

 

[three4rd]

Did you use well water to fill the pool with? Does it have a lot of iron in it?

Thanks for the reply. The water was purchased and delivered by a water supply company that specializes in filling pools. No metals present. Also, the discoloration problem only showed up near the end of this season, not last. Could it be some sort of efflorescence coming up through the coping and grout? I ask this since we have either a calcium and/or efflorescence problem with the tiles/grout. We do have a well but I only add water from it as needed. Also, we never had any similar problem with our previous coping and that was on for 25 years.

 

[JamesW]

Some granite contains iron and can rust.

 

[three4rd]

Some granite contains iron and can rust.

Well that's just wonderful....so what do I do about it?

 

[JamesW]

Don't know about solving rust stains on granite. I would suspect that the rust could come back over time. Maybe sealing would help.

 

[three4rd]

Don't know about solving rust stains on granite. I would suspect that the rust could come back over time. Maybe sealing would help.

Acid Magic is supposed to remove rust so hopefully that will do the job. I googled info on rust in granite and really can't find much about that. I have checked with my pool plasterer to see if he knows more about it. Thanks.

 

[JamesW]

Check with a good stone mason.

 

[YippeeSkippy]

Could it be some sort of efflorescence coming up through the coping and grout? I ask this since we have either a calcium and/or efflorescence problem with the tiles/grout. .

Efflorescence is usually white chalky looking in my experience. Often that is from moisture behind the cement. Usually a dilute Muriatic Acid solution will remove it, but I'm not sure you'd want to put that on unsealed grout?