Pool Water Chemistry (Warning: Can Get Technical)

[haze_1956]

If I understand the first chart correctly.

Red numbers denote - Level to low to kill bacteria or algae

Black numbers denotes - no bacteria but algae possible

Green numbers denotes - algae also killed.


If this is the case, perhaps you should switch the Black and Green colors.
A small point I know, but most people will associate the color green with algae growth. And it should help a layman to comprehend the chart.

[chem geek]

If I understand the first chart correctly.

Red numbers denote - Level to low to kill bacteria or algae

Black numbers denotes - no bacteria but algae possible

Green numbers denotes - algae also killed.


If this is the case, perhaps you should switch the Black and Green colors.
A small point I know, but most people will associate the color green with algae growth. And it should help a layman to comprehend the chart.

Yes, you understand the chart correctly. I was thinking of red being "bad" and green being "good", but I see your point that green, in the context of pools, probably means algae to most people. I'll change the colors in the table when I make some other changes I'm working on.

[haze_1956]

in the context of pools, probably means algae to most people

I personally made the "green means algae" association so I mentioned it.

But now you have me thinking completely in context of pools. How about these for full visual association?

Red = Germs
Green = Algae
Blue = Clean water

.

[aquarium]

If the pH is lowered to 7.2 do the charts change significantly?

[CToon]

THanks for taking the time to post this information. Having an understanding of the relationships is helpful

Following the Best Guess Chart has kept me out of trouble to this point. Through real world experience , I know it provides a margin of safety . I also know that things are better when I have FC towards the upper end of the scale. Now there's a little more insight as to how and why.

[chem geek]

If the pH is lowered to 7.2 do the charts change significantly?

I can best describe the change by an example. At a pH of 7.5, FC of 3.0 and CYA of 30.0 (and TDS of 550, Temp of 80ºF), the HOCl is 0.045.

At a pH of 7.2, with everything else the same, the HOCl is 0.052 which is not a huge change, but is still about a 15% change. The best thing to do is to download the spreadsheet and put in your actual numbers, but remember that except for disinfection, this is VERY preliminary so use with caution. Stick with Ben's best guess chart for now.

Richard

[chem geek]

I updated the PoolEquations.zip spreadsheet as well as the graphs and charts in the first post in this thread (and the links) to reflect the fact that FC (and CC and TC) are measure in ppm of Cl2 equivalent and not as HOCl. I also changed the HOCl concentration to also be in ppm of Cl2 equivalent so all chlorine is measured in the same way and this made the changes to everything rather minor.

I also added the Borax and Borates (ppm Boron) to the spreadsheet, though I need to do some cleanup to make it easier to use. I still need to replace the Solver calculation with my own iteration so that the spreadsheet will work reliably on a PC (it works fine on my Mac).

[EDIT] I made an initial error and have now corrected it so be sure that the first line of the spreadsheet not only gives the date 8/15/06, but also has the word "CORRECTED2" after this date. [END-EDIT]

Richard

[ubalr1]

I updated the PoolEquations.zip spreadsheet as well as the graphs and charts in the first post in this thread (and the links) to reflect the fact that FC (and CC and TC) are measure in ppm of Cl2 equivalent and not as HOCl. I also changed the HOCl concentration to also be in ppm of Cl2 equivalent so all chlorine is measured in the same way and this made the changes to everything rather minor.

I also added the Borax and Borates (ppm Boron) to the spreadsheet, though I need to do some cleanup to make it easier to use. I still need to replace the Solver calculation with my own iteration so that the spreadsheet will work reliably on a PC (it works fine on my Mac).

[EDIT] I made an initial error and have now corrected it so be sure that the first line of the spreadsheet not only gives the date 8/15/06, but also has the word "CORRECTED2" after this date. [END-EDIT]

Richard

Darn! The previous version was working fine for me (PC). Now this version gives me the "solver error". I must have installed it wrong, or did not remove the first one correctly. Any other issues reported with this new version.

Double darn!! The original version is no longer available. I can't even go back to that one. I'm drifting aimlessly now, I was getting very attached to that 'working' spreadsheet.

[chem geek]

I wasn't sure where to put this interesting piece of info, so I'm putting it here in the Pool Water Chemistry thread since it is related to the chlorine/CYA relationship. This link describes a patent where a fluid is initially viscous in order to carry particulate matter and then becomes less viscous (more fluid) over time in order to deposit or settle its particulate matter. The patent uses a thickener, a hypochlorite, and cyanuric acid. Differing ratios of the CYA to chlorine determine how quickly the thickener breaks down (which changes the viscosity of the water). It's interesting that this is a patent that DEPENDS on the chlorine/CYA relationship for its proper functioning in having only disinfecting chlorine (that is, chlorine not bound to CYA and probably only hypochlorous acid) break down the thickener and having that concentration (and therefore reaction rates) be dependent on the chlorine/CYA ratio.

Richard

[chem geek]

I didnt think this post deserved its own thread, but it is some useful info regarding ozone and chlorine. waterbear (Evan) and I worked out how ozone could oxidize chlorine since there were some reports of people using ozonators finding greater chlorine usage (loss). The following is apparently what happens:

O3 + H2O + 2e --> O2 + 2OH- ............ Eo = +1.24V
OCl- + 2OH- ... --> ClO2- + H2O + 2e .. Eo = -0.66V
-------------------------------------------------------------
O3 + OCl- ...... --> O2(g) + ClO2- ........ Eo = +0.58V
Ozone + Hypochlorite ion --> Oxygen + Chlorite ion

O3 + H2O + 2e --> O2 + 2OH- ............ Eo = +1.24V
ClO2- + 2OH- .. --> ClO3- + H2O + 2e .. Eo = -0.33V
-------------------------------------------------------------
O3 + ClO2- .... --> O2(g) + ClO3- ......... Eo = +0.91V
Ozone + Chlorite ion --> Oxygen + Chlorate ion

With the net result being the following:

2O3 + OCl- ... --> 2O2(g) + ClO3- ......... Eo = +1.49V
Ozone + Hypochlorite ion --> Oxygen + Chlorate ion

So ozone will oxidize chlorine to form chlorate. This is a very strong (likely) reaction, but the above info does not determine the rate of the reaction.

Richard