Quote Originally Posted by Jakebear
So ---- now I know what to do ----- but being who I am and the way I am , ----- I still want to know why the switch to Ultra Bleach caused the problem. And since I have no Copper or Iron ----- What the heck is it?
Marie (mbar) is an expert in stains so could probably help explain this with more real-world experience than I (so perhaps you should re-post your question in the Stains and Metal Matters forum), but it is known chemically that higher pH precipitates metals out of water and can therefore cause staining. Bleach is somewhat high in pH at 11 and Ultra Bleach may be slightly higher due to somewhat higher chlorine content (6-7.35% for Ultra vs. 6.15% for Regular Clorox bleach). Chlorinating liquid at 12.5% sodium hypochlorite concentration is even higher in pH at around 13.

When you add the chlorine to your pool, this higher pH may precipitate the metals in the region where the chlorine is "spreading out" from where you pour it. Eventually, though, the dilution of the chlorine in the total pool water volume will lower its pH below the level where precipitation will occur. If this is what was happening to you, then I would expect most of the staining to occur wherever it is you poured your chlorine. Is that the case? As for why no iron or copper is measured in the water, perhaps you precipitated it all out from the use of the chlorine -- either that or the stain is something other than copper or iron (a true mystery!).

Richard