Stains in Saltwater Pool - need help! Can't figure this out.

janglinivory

New member
Nov 8, 2020
2
St. Petersburg, Florida
Hello! I own a 8,900 gallon saltwater pool in St. Petersburg, Florida with a Jandy Pro Series TruClear Salt Chlorinator. We've had the pool for 14 months with minimal issue. It is an exposed aggregate concrete finish. Unfortunately, it is very near a giant oak tree so debris and leaves are an issue, but I've been diligent in keeping the pool clean... until...

I had to leave town unexpectedly for a week. About two weeks ago, when I returned, I shocked the pool as it was turning green - balancing the pH, alkalinity and using Suncoast liquid chlorine to shock. Did the usual brushing/cleaning filter twice a day. The water cleared... however, I'm still left with expanding stains on the bottom of the pool that will not brush away. Current readings, using the TF-100 test kit:

Total chlorine - 19ppm - no CCs - still high from becoming frustrated with the stains three days ago and adding additional liquid chlorine.
pH - 7.2
Alkalinity - 100ppm
CYA - between 70 and 80. I think this is high? I may have accidentally added too much stabilizer a few weeks ago.
Salinity is around 3,700 ppm.
Calcium hardness is 400ppm.

A pic of the stains is attached. This is the first pool I've owned... it was a "so far so good" exercise... but now this novice is in over his head. Any advice/help will be appreciated... I know there are some great knowledgeable folks on this forum.
 

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janglinivory

New member
Nov 8, 2020
2
St. Petersburg, Florida
Looks like iron.

Put a vitamin C tablet on a spot to see if it clears.
Thank you! I bought some vitamin C tablets today and, in various areas, either completely removed or very much faded any spots I tested.

What is your recommendation for a complete treatment of the pool? Do I need to reduce the chlorine level prior to treating? ...it is still pretty high (14-15ppm) from my previous shock.