Problems balancing water after using ascorbic acid, sequesterone and polyquat

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G

Gasolina

Well-known member
Sep 7, 2013
45
Tarano Lazio Italy
IG vinyl 19797.23 fc 0.1! Ph 7.5 cya 72 alk 75 ch 380 no reading for total chlorine at the moment, no borate.
apologies of this is covered elsewhere, but I have looked and can’t find an answer.
I have just attempted to remove iron stains from my vinyl pool, using ascorbic acid in conjunction with sequesterone and some polyquat to keep the algae at bay during the process, as fc has to be reduced to zero and ph lowered. I am also having to use a Scuba II photometer kit as it is sadly impossible to get any of the better kits in Europe at the moment and I have run out of reagents for my dpd pro kit.
The results on the staining are good but I now seem to have a problem. The Scuba II read free chlorine as 0.1 the day after completing the process above, with all other readings, as above quite normal. This morning I tested again. fc is still reading 0.1, which having added the bleach yesterday morning would seem impossible, especially as it was not a sunny day. My feeling is that either the dpd1 tablets sent with the machine are old, the machine is faulty or there is a legacy from using polyquat, sequesterone and ascorbic acid. Does anyone know if completely depleted chlorine is a result of using any of the above? I have contacted the vendor of the kit and requested a new one/ fresh tablets. I have added more chlorine this morning but am nervous of allowing anyone to swim as I really have no idea of the chlorine level.
I am really desperate to manage the pool water and am now relying on a test strip system which is impossible to read accurately. HELP!
 
It will take much more chlorine than usual to bring the FC up after an ascorbic acid treatment. You need to do this slowly and watch the PH level carefully as high PH risks precipitating the metal again. There is a good step by step guide here: Ascorbic Acid Treatment - Further Reading

Unfortunately good titration based test kits are difficult to get in Europe. I also rely on photometer based testing. If you are worried that your reagents or testing kit are incorrect you could do a quick "bucket test" where you add a measured amount of liquid chlorine to fresh water in a bucket and check the result.
 
Thank you very much for the info and the article. Much appreciated. I am relieved to know that the low fc could be the result of the ascorbic acid treatment. When you say much more bleach than usual- roughly how much more? Double the quantity? More? Over roughly what period of time? Does the polyquat affect the performance of the bleach? It is really difficult to find articles on safe swimming times after using the above items. Do you know of any good articles on it?
Thank you again.
Caroline
 
It depends on how much ascorbic acid remains in the pool after the treatment. Ascorbic acid is a chlorine neutralizer which is probably why you arent seeing a residual FC. Keep testing and adding small amounts regularly (e.g. 2ppm). When the FC level begins to hold it means the ascorbic acid is gone.
 
I did this treatment in the fall and it took a long time for my FC to hold. It kept dropping to 0 after I would add chlorine. You will get there ...
 
dbalzan said:
It depends on how much ascorbic acid remains in the pool after the treatment. Ascorbic acid is a chlorine neutralizer which is probably why you arent seeing a residual FC. Keep testing and adding small amounts regularly (e.g. 2ppm). When the FC level begins to hold it means the ascorbic acid is gone.
Click to expand...
Thank you. The Chlorine started to hold on day 3. However, I seem to be using more bleach than in previous seasons ( .876 us gall daily whereas usually it is about half that ) . Have read up about it and it could be that my PH is slightly lower than usual, but my CYA is 71 so the bleach should hold. Any ideas?
 
Make sure to backwash if you have a sand filter. I had lots of the AA in my filter and when I backwashed, it helped to clear it out. That helped my FC finally start to hold.
 

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