On Thursday, June 26, 2014 10:02:56 AM UTC-4, DannyD. wrote:
trader_4 wrote, on Thu, 26 Jun 2014 05:31:48 -0700:



I'd suggest that you're reading something from one source that even

they say is based on personal observation. IDK what they were observing,

but following that as if it were gospel doesn't sound too wise to me,

especially when the stds orgainzations, health depts, who's job #1 is

to make sure pools are adequately sanitized say nothing of the sort.



Hi trader 4,



I'm all for the truth, and, I do understand your argument that we

should look to the health departments to see what their recommendations

are for *outdoor* uncovered pools.



But, I do refute the assumption that there is only one source for

the CYA levels hindering the effectiveness of the free chlorine.



I never said there is only one source for the CYA levels hindering
the effectiveness of chlorine. In fact, I acknowledged that it happens.





I do agree that specific *chart* I referenced has few authors, but the

*science* behind the chart's assumptions is (apparently) sound.


The sciene we agree on is that it has an effect. That says zippo
about the soundness of that chart, which the author even states is
apparently made on his personal observations, whatever that means.

My observation is that with CYA in a range of 30 to 70 or so, chlorine
levels of 1 - 3 have not caused any problems in my pool. And I don't
know of anyone except you that has these high chlorine targets, 4 floaters,
etc.






The chart is an just a pragmatic attempt to make the known science

*applicable* to a pool owner. So, let's not concentrate too much on

the chart itself, and look to see if we can find official recommendations

for *outdoor* uncovered public pools.



Googling, for outdoor institutional pool chlorine recommendations,

I instantly find this "article", which discusses experiments

made at the outdoor Hall of Fame pool in Florida then at the University

of Hawaii outdoor competitive pool:

http://www.ppoa.org/pdfs/PrP_Cyanuri...0or%20Bomb.pdf



Again, that article (it's not a scientific paper but it lists about two

dozen scientific references) supports the theory that the CYA reduces

the sanitizing effectiveness of the chlorine by more than 1/3 at the

normally recommended levels of free chlorine (although it does discuss

the fact that bacteria do still die ... they mostly just die ten times

slower).


Look at figure 1 of the above document and you can see that what you're
doing is a waste of time. Look at 40 PPM CYA. With a chlorine level of
1.5 you get an effectiveness of 660. Take the chlorine all the way up
to 4, and you get an effectiveness of 730. It effects it, but adding
4X the chlorine doesn't improve the sanitizing ability that much.

Then look at 60 PPM CYA. You can take the chlorine to 4, or even 8 as
you are doing, and what happens to the effectiveness? It's almost the same
as it is with the chlorine at 1.5, ie the additional chlorine isn't
doing anything to help you.

And you don't need super effective chlorine, you just need enough to do
the job. If X works, 2X or 6X isn't really going to work better, for routine
sanitation. And apparently with 60 CYA, 2 PPM chlorine is fine, except
apparently for the guy who came up with that chart.

Note that the above article you found, the author doesn't say that
you need 6, 8 whatever chlorine, like the chart you found. And as I've
pointed out, those levels are way beyond what every public health
authority I've seen recommends. If anything, it's more likely you're
going to find someone saying those levels are too high for the pool to
be used.