Yellow-Brown Stain in the Deep End

[Drsafety]

Hello. I have been following the trouble free pool method since 2013 with success! Well, after adding a few 40 pound bags of salt, I have my first mystery. After the salt dissolved, I noticed a yellow-brown stain in the exact spot where the salt was dumped. I have tried brushing the stain away with no luck. The salt was Diamond Crystal (blue bag). Thoughts? Thanks!

FC 7
CC 0
PH 7.5
TA 70
CH 175
CYA 60
Salt 3400

 

[Drsafety]

Here’s my signature...
20 x 44.5 single roman end, ~33,000 gallons, 10 feet deep, garrett vinyl liner, Hayward SwimClear Cartridge Filter, Hayward 2 HP Pump, Cirrcupool RJ60 SWG, Hayward 140k BTU Heater, Polaris 380 with Booster Pump

 

[JamesW]

Probably iron from the salt.

Try vitamin C on it.

 

[revitup]

Iron stains from salt? Is that a thing?

 

[JamesW]

It's a thing.

Instant Stain

I don't have current test results yet, but hope someone can point out what possible interactions may have resulted in this. I don't close the pool for the Winter, but other than checking salt now and then I just let it run and verify balance of things before starting to use it again. Yesterday...

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