I have the TF-100 kit, it has worked well all summer. I have an issue that I'm puzzled about. My chlorine testing tube has gradually acquired black residue on the sides, and my chlorine power itself has turned black.
I've been obsessive about trying to keep the powder dry, so I don't think any water got in there. I rinsed the tube and scooper after each use as well, but they still turned black. Is this normal? The powder seems to still work just fine even though it's discolored. I need to buy some replacement regents, but I want to avoid this happening again. Any ideas?