The fungicide, tebuconazole, in the Bayer product is stable indefinetly at all pH vaules. Mancozeb, on the other hand , is very unstable at alkaline pH values:

pH 9 (0% remaining after 2 hours)

pH 7 (25% remaining after 2 hours)

pH 5 (62% remaining after 2 hours)

If your tap water is alkaline, it clearly pays to adjust the tapwater pH to an acidic value before adding Mancozeb. A commercial product, Indicate 5, can be used to do this. It contains an acid and a pH indicator dye that turn blue when you've added enough to change the pH of your tapwater to about 5. A cheap substitute is to simply add about 3 tablespoons of plain (5% acidity) vinegar to each gallon of tapwater. This will change the pH value to roughly 5 for essentially all potable tapwaters. To be on the safe side, you might check with some pH paper, but I doubt that that is really necessary.

Mike,
Don't you mean pink? I think Indicate 5 is really great - convenient and has a surfactant in it (spreader/sticker) as well.

Rocky, Indicate 5 does turn pink, not blue, when the water pH reaches 5, according to the Rosemania site. I was going by memory and that's sometimes risky at my age (I use this excuse a lot).

It's a good thing you don't have to buy baby clothes!

Many thanks friends, for the help. I am learning so much from you all.
Mel