stain removal

[poolhelp101]

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tell me what i done wrong and how to fix. i had stains on my pool and i used the asboric acid method to remove. chlorine was at zero when i done the asboric acid. the stains vanished just as the instructions stated. the pool was perfect. the next day i added bleach to start to bring the chlorine back up and everything still good. two days later, today, i notice the pool started to have a green tint. i added polyquat, and more bleach as the chlorine was showing very little. the pool is getting more and more green. one thing i did forget to do when i was using the absorbic acid was add metal out. is this what i done wrong? should i add metal out now?? the only other thing i done right after i used the asboric acid was to turn on my heater. did that have an effect on it? i have a 21,000 gallon inground, sand filter. please tell me what steps to take to get the pool back on track. thanks.

 

[Guest]

ascorbic acid is a reducing agent (anti oxidant) which is how it gets rid of metal stains. It changes their oxidation state to a colorless, soluable one. It also destroys chlorine, which is an oxidizer. Eventually the chlorine oxidizes all the ascorbic acid and the chlorine holds but until it does it is next to impossible to hold chlorine in the pool. This is why you need to add the minimum amount of chlorine several times a day until it hold. Otherwise algae starts to grow (In hot weather it does anyway, which is why I usually say don't do a stain removal treatment until the weather is cool). Turning on your heater made the conditions more favorable for algae to form.
You cannot shock because that would oxidize the metal sequestrant you added to keep the metal 'deactivated' and also oxidize the metal back into it's colored form that is insoluble. It then reforms the stain on your pool or colors the water yellow. (ascorbic acid is most effective on Iron so I am ignoring copper and manganese here.)

 

[frustratedpoolmom]

Yes, add the sequesterant. Then several times a day, keep adding small amounts of FC (you dose to the "min" for your CYA level). Maintain maintenance doses of Polyquat.

You'll have to do this routine for 2 weeks, adding several bleach additions throughout the day to try and stay ahead of the algae. Since you can't shock for 2 weeks. You may still have algae when all is said and done...and have to shock. Keep up on your sequesterant and PQ60 dosing. Be diligent in checking chlorine to keep it at the "min" level.

Or you could shock now, kill the algae, possibly stain the pool again, and repeat the stain removal process when the weather is cooler and swimming isn't a priority?