Breakpoint Chlorination

[chem geek]

First regarding the book that talks about forming monochloramines to help kill the algae, well this is true that you'd be forming a LOT of monochloramines with that method. But you WON'T achieve breakpoint chlorination without adding a lot more chlorine (unless I screwed up in my calculations).

As for BleachCalc, yes it is "technically" wrong, but as you can tell it's not wrong by much and the error in measuring cups plus the degradation of chlorine over time means that you probably do need to use a little more to end up with what you expect. WHOOPS! This means the error in BleachCalc is in the wrong direction! BleachCalc probably has you add even less than you need rather than more.

Also, the density of the 12.5% liquid chlorine being 1.16 g/ml is not true for bleach which is probably closer to water density, probably around 1.07 g/ml, so BleachCalc would be even a little more "too high" in this case (that is, reporting that the change in ppm is more than it really is). I have verified my calculations with my own pool and the use of 12.5% chlorine to the extent possible, but this isn't easy since I do suspect that the chlorine does degrade somewhat at the pool store.

Mmmmm. I think we need to verify this with some more real-world experience before we get Michael to change BleachCalc. What is your experience?

Richard