Pool Water Chemistry (Warning: Can Get Technical)

[stualden]

These are great - personally I find I need to stare at them quite a while to grasp them (I guess it's because you're dealing with 3 variables on two-dimensional graphs) but they convey more than words can.

Just a couple comments / question for clarification:

--What are the numerical values corresponding to "algae" and "bacteria" on your first graph? Do they correspond to the colors of the numbers in the table (i.e., red is below bact, green is above algae, black is in between)? Do these levels of HOCl correspond to particular levels of "oxidizing power" or "disinfecting power" that we commonly see quoted?

--Taking that algae line as a given, I read (roughly) the following minimum chlorine PPM for various CY PPM:

CYA..........Chlorine
5...........1
10..........2
20..........3
30..........4
50..........6

(Could you do another graph or chart which transforms the data into this format?) Unfortunately, these look even a bit higher than Ben's chart - discouraging!

--On the second graph, would you say the "take-away" is really that most of the chlorine-retention benefit of CYA is *already there* by 20 ppm, rather than "starts at" 20 ppm?

--The "no CYA" and "infinite CYA" entries are really points, right, not horizontal lines? (Hard to show clearly on this graph, though, I'll agree.)

--You talk about the "half-life" of chlorine, which gets at a concept you mentioned in that other post and I asked about there. I'm assuming that half-life here means the time in which the free chlorine ppm drops to 50% of what it was before. Perhaps you could also recast this graph to illustrate your point that "with twice as much chlorine, you lose it twice as fast." To me, this emphasizes the "double gotcha" with CYA - it forces you to bring your chlorine levels higher, which in turn means that your chlorine loss each day will be higher.

Thanks.