Mysterious staining on quartz finish

[dgoloughlin]

Hi there,

I'd like some advice on some staining that's occurred recently on an established quartz finished pool.

It seems to have been triggered by the addition of pool salt but I can't really say for sure as you can't see the stains in full sunlight and I didn't see the staining straight away.

When I saw the stains properly for the first time I assumed it was because of iron and I treated the pool with ascorbic acid followed by a phosphonic acid based sequestrant. I've had success with this in the past but this time it did nothing.

I then did a spot test using dry acid and this worked but since the quartz surface is textured the result is quite blotchy.

Here are my vital stats, I'm reasonably careful with water chemistry but chlorine levels and PH are often on the high side while alkalinity is on the low side.

Salt: 3800
FC: 7
TC: 8
PH: 7.4
Alkalinity: 40
Calcium: 175

I've also attached some photos (apologies for the shadows) and as you can see the finish looks dirty and blotchy.

Many thanks,
David

 

[Texas Splash]

Hello David. Since dry acid worked, I might initially be concerned with copper. Your signature is blank. Do you use a mineral system or and copper-based products in your pool?

 

[dgoloughlin]

Thanks for your reply.

No I have a SWG system and have never used a product with copper in it.

It could have been introduced with the salt though, we had very high rainfall in my city over summer and it was difficult to find pool salt anywhere. I had to use lower quality stuff.