bleach use and metal

[SHADEZ]

I've read that metal staining can show up or occur after adding liquid bleach .. why, what causes this .. is it one of the by products in the bleach or is it a combination effect with other things in the pool that brings it out?

When adding liquid bleach should I use a sequestrant at the same time? Should it be added before or after adding the bleach?

Since sequestrants breakdown .. is there a sequestrant test?

 

[chem geek]

It's the rise in pH when you add a hypochlorite source of chlorine that is the primary cause of metal ions forming metal oxides/hydroxides/carbonates that can stain. Adding a metal sequestrant before adding chlorine can help as can lowering the pH first before adding chlorine. If you add the chlorine slowly, then you can usually see if a problem is developing and stop it before it gets worse. Lowering the pH back down usually reverses any staining that just gets started.

Also, if there is no chlorine in the water, say from a fresh fill of well water, then the chlorine can oxidize solid iron as well as ferrous iron ions (Fe²⁺) into ferric iron ions (Fe³⁺) that can then form oxides/hydroxides/carbonates that can stain.