Another view on CYA

[Tredge]

Interesting read.

Somthing I noted about the study. They take snapshots of pools, points in time.

If you were to do a study over the life of a pool at 100ppm CYA, I think you would find that it drifts in and out of satisfactory ranges more often than one at a CYA of 50-60.

The reason for this is that a high CYA pool IS still killing the bad stuff....just slower. At peak activity the high CYA pool may not keep up even if it stabalizes back to a satisfactory level given time.

Also they dont show how they test the water....did they test for bacteria levels instantly or send it to a lab and test after several hours. A High CYA pool and a low one will score the same over a period of time.

I dont like bacteria and viruses to live for a few minutes let alone hours.....I dont care if they die eventually...I want them to die Now!

[CarlD]

I only glanced at it quickly--I see so many darned statistical studies (I work for a C.R.O. and we work with pharma companies on clinical trials every single day) that I spotted some things that had me curious.

1) How could a model ONLY see FC as relevant and not the FC/CYA relationship?
2) Why do they seem disparaging of the TOUGHER standards of sanitation? NOBODY goes in my pool unless it's at those tough standards.
3) Most of the graphs have dip in them where the slope actually changes directions. It's consistent across many of them them--and in the same spot. This doesn't make sense. FC rises and bacteria falls, THEN rises, then falls again? It's not just in one graph, so it's not an abberation. I suspect it's a flaw in the model--probably the sampling procededure. Since it's across what? 450 pools approx, something is happening they aren't addressing.

Again, I haven't looked closely but 3) is SO odd that they should have an explanation of it---and don't. I'm also no whiz at modelling, but I DO know a little about it.

[gonefishin]

Summary
The results of this study clearly demonstrated that:
• Free chlorine has by far the greatest influence on the disinfection conditions and the incidence of algae in pools than any other variable.
• Other variables can affect the disinfection conditions but their effects can be easily controlled by maintaining free chlorine at the appropriate concentration continuously.
• Swimming pool operations that use a 1.0 - 5.0 ppm free chlorine range have a greater probability of being bacteriologically satisfactory for swimming than those that use a 1.0 - 3.0 ppm range.
• Higher (3.0 ppm or more) free chlorine concentrations are required to reduce the incidence of algae than are required to maintain adequate disinfection conditions.
• High cyanuric acid did not negatively impact the disinfection conditions or the incidence of algae.

In the last statement of the summary they go on to say that the high cyanuric acid levels did not negatively impact the disinfection conditions or incidence of algae. Yet...they found it necessary to raise the disinfectant levels from 1-5ppm to 3ppm-or more when there was a presence of algae.

I would rate the study inconclusive at best.

dan