Pool Water Chemistry (Warning: Can Get Technical)

[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]

ubalr1,

I'm sorry you now get the Solver error. I assume this only occurs when clicking on the "Calculate pH/TA" button, right? This has been reported as very flaky on a PC and I was able to reproduce the problem on a PC and it sometimes would work and then it wouldn't, so I don't think it's only the version change but something very strange with PC's solver getting a spreadsheet created on the Mac.

I plan to replace the use of Solver, but am going on vacation (to Canada) for 2-1/2 weeks. I'm taking my computer and one of the things I'll do during down time (on the train, for example) is work on the spreadsheet. Yes, I consider that fun (shows how geeky I am).

I don't have the earlier version myself anymore. As soon as I replace the Solver with my own iterative code, I'll post it and let everyone know by a post to this thread. Again, sorry you got "hooked" with a working version. It's pretty neat when it works, eh?

I just put up the latest version just in case that one works for you. You can download it and try it out.

Richard

[chem geek]

ubalr1 and others,

I just removed the Solver dependence and uploaded a new (modified) spreadsheet. Give it a try and let me know if it works. Unfortunately, it will still "think" that Solver is being used when you load the spreadsheet so it will give you two macro warnings and may require you to add the Solver Add-In, but it won't actually use the Solver itself (which was the main problem).

[EDIT] As of around 8/30/06 I removed the apparent reference link to Solver that made Excel think that Solver was used even if it wasn't. [END-EDIT]

Richard

[ubalr1]

ubalr1 and others,

I just removed the Solver dependence and uploaded a new (modified) spreadsheet. Give it a try and let me know if it works. Unfortunately, it will still "think" that Solver is being used when you load the spreadsheet so it will give you two macro warnings and may require you to add the Solver Add-In, but it won't actually use the Solver itself (which was the main problem).

Richard

Hope you had a fine vacation Richard.

The speadsheet is working fine for me now. I had to uncheck the Solver in "Add-Ins". Thanks.

Couple of questions:
1) Can I change the concentration of Sodium Hypo? You have 11.9% in there. I use the 6% bleach.
2) I don't know what my Total Sulfates or Total Borates are. Can I still get accurate results using the spreadsheet?

[chem geek]

Hope you had a fine vacation Richard.

The speadsheet is working fine for me now. I had to uncheck the Solver in "Add-Ins". Thanks.

Couple of questions:
1) Can I change the concentration of Sodium Hypo? You have 11.9% in there. I use the 6% bleach.
2) I don't know what my Total Sulfates or Total Borates are. Can I still get accurate results using the spreadsheet?

I finally figured out how to remove Excel's thinking that there were references to Solver (when there weren't any more) so will update the spreadsheet with that fixed soon [EDIT] just uploaded an update today 8/27/06 with the Solver references removed [END-EDIT] [EDIT] and again today 8/28/06 with further improvements listing different concentrations for bleach in a pull-down menu. [END-EDIT]

Yes, you can get accurate results without the Total Sulfates or Borates entered, unless you have intentionally added lots of Borates (say, more than 30 ppm). The sulfates are there in case one has very high sulfate water (> 100 ppm) in which case this starts to affect the calcium carbonate water balance.

Richard

[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