Firstly I read this post in the "Deep End" on this forum:
I found it interesting and decided to give it a go as ChemGeek found no real issues with it
And a word of warning I would like ChemGeek to review what I have written and make comments on what he likes and does not like before any of you go charging off and doing it. Just because it worked for me in my particular set of circumstances it may not be appropriate for you.
Please note carefully: my 10,000 gallon pool is 16+ years old non-colored plaster salt water pool. The non-colored part of the warning maybe important, colored plaster can sometimes stain with some chemicals.
A little history follows; before Xmas perhaps late November I did the normal AA treatment for iron substituting a small amount of Hydrogen Peroxide to reduce my chlorine from around 5 to zero instead of using Thiotrine. After the treatment I increased Jack's Magic Purple Stuff to 40 ppm as a base amount from 30 ppm. Since then I have had a much slower accumulation of noticeable iron stains than I normally had in the past. Unfortunately since then we had two separate weeks of very high winds, in excess of 45 mph and as high as 60 mph. This as is normal resulted in the deposit of large amounts of wind born dirt much of which contains volcanic dust (which also contains a fair amount of iron oxide) and organic debris . In those two separate weeks I made sure the sequestrant Jack's Magic Purple Stuff was maintained at 40 ppm.
Despite maintaining the following numbers, small shadows started to appear in the pool particularly in the last few weeks and while not noticeable to those unaccustomed to our pool I noticed them. So I decided to do an iron treatment but based on the above post in the "Deep End" I thought to try out the "Hydrogen Peroxide Method" as it does not affect the pH and as I already keep it at 7.3 to 7.4 anyway it would create less work to re-balance it back from the normal 6.6 to 6.8 that results after the AA treatment. I did lower the pH to 7.2. The numbers before starting looked like this:
pH 7.2 (normally 7.3 to 7.4)
Borates 0 (dog)
Phosphates are well over 20,000 ppb but they are no trouble so long as the Chlorine is kept at 5 or above (max 9) or I have problems getting a pH reading.
After the sunset (to avoid an algae bloom) at around 7pm, turned the SWG to zero percent production and added 126 ozs of 3% Hydrogen Peroxide, which lowered the chlorine from 6ppm to zero. I then added an additional 178 ozs to act as a metal stain remover/oxidizer. The pool pump ran all night, as the pH does not change with Hydrogen Peroxide, I did not have to bypass the heater or remove the in-pool suction cleaner.
In the morning before dawn about 5:30am I added 8 oz of Muriatic acid and two large 184 oz jugs of Chlorine. After two hours with pump and cleaner still running I returned and the pH was 7.3 and the chlorine read 6 ppm. All other numbers remained the same.
Now the results, well the pool looked OK for the most part. The stains that were there were hardly visible to the naked eye but they were very faint so I knew they were there. So I thought OK but not as good as AA. Now 4 days later even the faint stains are nearly impossible to see unless one knows what to look for. Interestingly I have one 16 year old fisheye which I have never replaced, it had a dark greyish/yellow stain on it's movable ball on the underside which was quite noticeable if turned towards the surface, that stain had never been removed by the AA treatment, nor by chlorine shocking, but now the small stain is nearly gone, especially the grey cast; it is now a very faint yellow.
I am not sure why as these four days have gone by it is still cleaning but it is. My guess is that it must have reacted not just with the iron but also with the organics and/or another metal type stain, or it lifts the stains so that the chlorine and sequestrant can do their work better. The temperature was not high and we have not had a lot of sun. I believe that Hydrogen Peroxide breaks down in sunlight, my only guess perhaps, and it is only a guess, is that with a high CyA of 80 it is somewhat shielded from sunlight breakdown, so in non SWG pool with a lower CyA it might breakdown too quickly and more Hydrogen Peroxide might be required.
Note: Virtually no sequestrant was used up in this process when I took a reading four days later.
As the reader might note the temperature was a low 70F, and the Hydrogen Peroxide had only a strength of 3% and I did not use that much deliberately as this was a first attempt. And I did not want to spend a lot of money on replacement chlorine to bring it back up to 5 or 6 ppm, after the normal AA treatment I always use up 6 jugs of chlorine or more until it gets fixed at 5 or 6 ppm, why I do not know.
Nevertheless the results were very good after 4 days, nearly as good as AA and in some ways better, and I am happy. I might go for more Hydrogen Peroxide, maybe twice or three times the strength next time, to see if all the virtually unnoticeable light remaining iron stains can be removed. Nobody else seems to see them except me, in fact my friend thinks I am seeing things that are not there, but they are.
I could not find the 27.5% stuff here in Honolulu at any of the local pool stores. Someone told me a medical supply house may carry it, known as 30% Hydrogen Peroxide . The local industrial chemical supply house has 50 gallon drums of 50% but that is a little over $500, and therefore too expensive.
Finally I still think AA is an excellent quick fix to persons with just iron as an issue, and most probably gets rid of most if not all the iron stains. However if wind born dirt or other unknown stains, not removed by the AA treatment, are also an issue this perhaps is worth doing. Indeed I might mix the two together IF AND ONLY IF Chemgeek thinks that is OK, or do Hydrogen Peroxide on day one and follow with AA a few days later, after rebalancing the water as I have done here.
Hope these results are of interest and of help to those with these issues.
Good Luck but wait for ChemGeek to comment or issue warnings before proceeding, and you may have questions for him.