"lighter" colored or blue stains in gunite pool trying to determine cause

[NSBFAN]

Hi all. These "stains" for lack of a better word have been present since I bought the house two years ago so I'm not sure how long they have been there. Here is the situation: my pool's plaster finish is a sand/tan color and so in the shallow end the water reflects little blue color but of course is more blue toward the deep end. Starting at about the 4' depth, there are these areas that look more blue and they continue in a random pattern to the deep end at 6 feet. Since my pool water has been so fantastically clear (thanks to everyone's help here at TFP ) it is noticeable.

It is not something that brushes off. It does not feel different to the touch.

I have no idea what may have caused this. Before me, the previous owners had a weekly service for the 8 years they had it (was built ten years ago). So who knows.

Attached is a pic - I don't know if the small resolution will show it here. I have others as well if it helps.

Thanks!

 

[YippeeSkippy]

Re: "lighter" colored or blue stains in gunite pool trying to determine cause

Ok... lets do these quick and easy tests: Take a chlorine puck (you can buy them individually or bum one off a neighbor) and rub it on one of the stains for a few minutes. If the stain lifts- its organic.

Then.. take a bunch of cheapo Vitamin C tablets and put them in a thin sock and rub that on a different stain than the one you did above. If it lifts it, its metal staining. And that often means someone used copper containing algaecide or the fill water came from a well with metals....

Let us know if either of these tests alter anything?

 

[NSBFAN]

Re: "lighter" colored or blue stains in gunite pool trying to determine cause

Thanks for the advice! I do want to clarify, however, that the dark color is the actual pool finish color. the lighter, or more "blue" is the issue - either stain, or variation in color - that is what to be determined.

My finish looks like tan sand. It has a sand color along with tiny aggregate of various flecks. It isn't pebble tec, but not just plain plaster. I'm not sure exactly what it is.

On the deep end step and seat area there is variation in the tint of the tan color, almost as if it was variation in the application. I'm wondering if that is what I see at the deep end - it looks more blue because of the water's effect at depth.