Pool Chemistry HELP!!!
- Thread starter flbranham
- Start date
- May 23, 2015
- 24,558
- Pool Size
- 16000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
I’m wondering if your permanganate injection is causing the positive interference you’re seeing. The purpose of the permanganate is to regenerate the green sand by restoring the manganese dioxide catalyst (the catalyst is what causes the dissolved iron to precipitate out). It would normally be flushed out of the media during the regeneration cycle through a series of rinse steps just as brine water is flushed out of the ion exchange resin of a water softener that removed hardness (Ca and Mg hardness).
The permanganate is a powerful enough oxidizer that it could produce either hypoiodous acid (HOI, similar to hypochlorous acid) or the triiodide (I3[-]) anion both of which can react with DPD and turn it pink again. So I suspect, but am not entirely certain, that there must be some interference going on with the CC portion of the test due to the presence of permaganate or manganese in general.
Do you have any water analysis (independent of the company that sold you the softener) to know how much iron and manganese is in your well water? The softener company is potentially an unreliable source of info because they have a motive to sell you something and say that it’s working fine. I’d want samples sent to an independent lab to verify that it’s all working.
The permanganate is a powerful enough oxidizer that it could produce either hypoiodous acid (HOI, similar to hypochlorous acid) or the triiodide (I3[-]) anion both of which can react with DPD and turn it pink again. So I suspect, but am not entirely certain, that there must be some interference going on with the CC portion of the test due to the presence of permaganate or manganese in general.
Do you have any water analysis (independent of the company that sold you the softener) to know how much iron and manganese is in your well water? The softener company is potentially an unreliable source of info because they have a motive to sell you something and say that it’s working fine. I’d want samples sent to an independent lab to verify that it’s all working.