After several uses the P/P tanks are red with iodine, pour some out and add peroxide or Sodium hypochlorite(pool chlorine) or clothed washing bleach. The bleach has some advantages over the others in that it has a bit of detergent in it , this is important to remove some of the oils in the p/p water.
How much to add? a lot of 3% peroxide, not very
much of the 33% peroxide
nit very much chlorine is needed
Just add it slow and swirl the mixture look for
the clumping up of crystal Iodine, let it setttle, then wash it in
water , dry it like tincture
The reaction waste water has varying amounts, add a little HCl or H2SO4 until the mixture just begins to turn brown them add the peroxide or bleach