Will Copper affect my attempt to raise pH?

[JWB]

Hi,

Can anyone tell me if a high concentration of copper in the water reduces soda ash's ability to raise pH? I have copper-induced vinyl liner staining all around my pool and have ordered a metal sequesterant. So far, I've added 18 lbs of soda ash through the skimmer. All it does is end up on the bottom as a blue silt, without seemingly doing much to raise the pH. Is there a correlation between the two?

Thanks,
Jon

CL 9
pH 7 (could be lower since my CL is way up)
TA 90

[chem geek]

Copper carbonate, as shown here, is not very soluble in water so with high copper concentrations adding soda ash (sodium carbonate) could precipitate copper carbonate.

If you want to raise the pH without this effect, you can use 20 Mule Team Borax instead, but keep in mind that with high copper levels a higher pH can cause copper oxide or copper hydroxide staining.

It would be better for you to keep the pH low and add the metal sequestrant before trying to raise the pH.

Richard

[JWB]

Hey thanks for the information. Actually I forgot, I am using Borax now. I started with 6 lbs. of ash but then switched over. Same result. I'll hold off until the sequestrant arrives.

I might need to use an ascorbic acid treatment to treat these stains. Would you recommend waiting to raise the pH until that's complete too?

Jon

[chem geek]

Yes, I'd wait on raising the pH unless it's very low (below 7.0). Just note that the ascorbic acid treatment will lower the pH further so when you are ready for that you may want to raise the pH some, but between now and then the pH may rise from normal outgassing of carbon dioxide (unless you are using an acidic source of chlorine such as Trichlor).

[waterbear]

actually, if you will vacuum the blue precipitate to waste you will remove some of the copper from your pool so it's actually a good thing.