Thank you for the reply. I changed the log to base 10, and as I am sure you know if you created that simple spreadsheet the phosphate numbers would have to exceed 117,000,000
ppb to create an issue; even I did not exceed that high number with a number slightly in excess of 65,000 ppb or 0.06% of that high figure.
I then did a little more research on the web and calling Dow, the "Stability Index" is based on the "Stiff & Davis Stability Index" used for high salinity situations based on TDS in excess of 10,000 mg/L, or if you like the index is used primarily in the desalination of high-salinity brackish waters and seawater desalination, obviously not appropriate to freshwater and saltwater swimming pools with a low TDS measurement.
So this equation will not work for us.
Dow Paper is here:
I wished I had "Googled" a bit more before I posted that paper, but learning from mistakes can have its benefits. It seems that maybe the 11.755 number has something to do with "Temperature coefficients for pH in seawater" the numbers seem close to these numbers mentioned in this paper on page 681, here:
As to the the 0.65 number in the original paper I linked to, here:
I do not know how that relates in the formula but I will ask Dow Chemical, they have been very fast at getting back to me. So I will ask them how these numbers were derived and can they be altered in a low TDS, non-seawater situation. My guess would be not very likely, but we will see.
Fortunately for me they treat me, as do you, as an inquisitive child and again, like you, they let me follow my hunches without blowing me out of the water and damping my enthusiasm to get to the bottom of this issue.
What I have learnt so far while both "Experimenting" and "Googling":
1. Orthophosphates can create scaling issues in sufficient quantities see this article on boilers (reading on beyond page 72 is also very interesting:
It seems that any where from 10 to 40 ppm, or 10,000 to 40,000 ppb might/can/will create "Calcium Phosphate Scale". As boilers operate at a considerably higher temperatures than a swimming pool would not then these threshold figures of 10,000 to 40,000 ppb be lower for a swimming pool?
Also low alkalinity can create the potential for scaling but I think most persons are aware of that.
2, From "Googling" and "Personal Experience" it seems that Hydrogen Peroxide in the presence of HEDP,above an HEDP level of 13 ppm (as I lost 20+ ppm in the process it might be best to start with a level of say 40 ppm), and if the temperature is ideally 70 F or below will remove "Calcium Phosphate Scale" and possibly just plain "Calcium Scaling." It is best performed in conjunction with a pH lower than 7, I used Ascorbic Acid (around 6.6 to 6.8). In my case quite spectacularly.
3. From "Googling" and "Personal Experience", it seems that at a temperature nearing or above 77 F HP does not work as well, some articles state it will not work at all if HEDP is present above 13 ppm and temperatures exceed 77 F. I have not tried that.
4. For the HP method to work apart from the above prescribed parameters iron and/or orthophosphates must exist in sufficient quantities to create a catalyst.
5. At present nobody, it seems, has worked out what the upper limits for phosphates in a pool are before "Calcium Phosphate Scaling" will occur. Although the above paper sets the lower limit at 10,000 ppb in a boiler so maybe half that say 5,000 ppb in a cooler swimming pool. This of course is a wild guess for safety's sake.
6. I still think that when person's answer the phosphate question and are told not to worry about them so long as chlorine and CyA are kept in check that this is wrong headed. One must tell them how to properly know their phosphate level by proper dilution and go from their. I agree my pool gets a lot of wind but so do some other pools and even though my level was for most of the 1 1/2 years was kept at a sequestrant level, using HEDP at 10 ppm, the phosphates rose to over 65,000+. Many persons just doing the test without dilution will assume it is 1,000 ppb or 2,500 ppb depending on the "Phosphate Test Kit" they use, and this can prove to be a serious issue as regards scaling.
7. A question. Is it conceivable the in the process when the oxygen molecule is released from the HP it remains in the pool longer as HEDP is present and helps oxidize both phosphate and iron?
I do not know if this article can bring any light to that question but here it is anyway from Columbia University:
8. Since I last wrote a few days ago my HEDP level has fallen from 80 ppm to 38 ppm, why I do not know. Any ideas? The filter has seen no increase in pressure but I did add 27 oz of CyA to up the CyA level from 60 to 80 about 3 or 4 days ago. The leaf canister nylon type filter material has lightened from a light medium brown to off-white, new it is white. The "Phospate Test still reads around 1,500 ppb.
9. One interesting thing happened this morning, one of those long garden slugs had fallen into the pool overnight, unlike all previous occasions it did not leave a stain. I think this has something to do with the "Calcium Phosphate Scale" being removed.
10. Nearly forgot the HP method in the manner described above removes a lot of orthophosphates, 63.500+ ppb in my case going from 65,000+ ppb down to 1,500 ppb over 4 treatments. Agood benefit to those with high phosphates.
Still no news on Thorium Nitrate the lady at Palintest said she was upset because the UK manufacturer had not gotten back to her.
The Pool looks really good and despite the pH rising above 7.5 there was no iron separation, it is now back down to 7.3