Looking for opinions on what caused these stains in a gunite pool...

[Swimmingly]

Hi all,

I'm new to both this forum and pool ownership. I would like to get your experienced opinions on what might have caused these stains in my pool. I have a 7,000 gallon gunite pool which has been under the care of a local pool company. The pool is almost 2 years old (though I've only owned it a short time) and it has looked beautiful until very recently. I left town for 6 days and upon my return, I found these big splotchy stains in the bottom of the pool (some sprinkled stains on the steps too).

I'd appreciate your thoughts as to what could have caused this.









Thanks!

[Denniswiseman]

If your pool is under the care of a pool company why haven't they dealt with it unless you have taken it over yourself
I suspect that it is Algae as it only developed over 6 days
Try rubbing a trichlor puck over it and see if it removes it, if it does it's organic (algae) if not rub some ascorbic acid over it (vitamin C) if it does it's mineral (metal staining)
The other thing it could be Calcium. You would need to use Muriatic acid, pour a little over a shallow part of the pool (steps) and see if it goes. Don't leave it there to long as it will eat into your surfce
How do you test (strips and pool store numbers aren't that accurate)
Can you let us have a full set of numbers
FC:
TC:
pH:
TA:
CH:
CYA:
Pool chemicals:
My pump & filter:

[Swimmingly]

Thanks for the reply Dennis. The pool is still under the care of the pool company and I am trying to get them to rectify the issue. Since I am so new to pool ownership, I'm looking for second opinions. The pool company has been reluctant to take ownership of the issue.

Regarding the numbers, I can only provide you with what they provided me with just prior to and just after the stains appeared:
Prior to stains: 3.0 free chlorine, 3.0 total chlorine, 110 total alkalinity, and 7.8 PH
After stains: 1.0 free chlorine, 1.0 total chlorine, 100 total alkalinity, and 7.8 PH

I forgot to mention that there were no stains on the sides of the pool. Only the horizontal surfaces (bottom of the pool and steps) were stained as if something settled on them. The pool company blamed it on calcium but one of the pool guys blamed it on di-chlor and said "someone screwed up".

[Denniswiseman]

You don't mention CYA as the amount of Chlorine in your water is relative to your CYA and high CYA renders your chlorine ineffective
You don't mention what chemicals you use either
For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm
You really need to get a test kit and test yourself (Taylor or TFT)
If this only happened over 6 days and "someone screwed up" it's up to the pool company to sort it out as they have been dosing your pool with what ever chemicals were needed
BTW have you tried the steps I suggested