I think you guys are pretty much on the same page.
Gary and I disagree on several things about water treatment. He likes chlorine, I don't. I use Potassium Permangenate and he doesn't.
Of course, he and I are about as far apart North and South as we can be. Water is different depending on where you are. What works for one area might not work so well in another area.
I don't think you could drink enough PP from a backwashing iron filter to hurt you, or we would have heard of at least one instance of someone being poisoned. I have never heard any such claim.
If you drank a little pink water, your teeth would be just fine as would the rest of you. However, stick your hand in the PP feeder and it will turn brown for sure.
I'm with you Gary, back to work.
bob...