Quote Originally Posted by CarlD View Post
(1 ml in 10 liters of water is the same as putting 1 gallon of LC in a 10,000 gallon pool -- it's 1/10,000th. )
Carl,

I'm prompted from the thread I started about cost vs % and the 'discrepancy' issue that rose up there.

From your suggestion, there, I did my first "Carl Method" testing and I liked it...and it made sense to me...and the more I thought about it...It's just like getting a test result from a 10liter pool. The ratio of the 1ml vs 10liters is linear. I could do the test at 5x the original volumes and get the same effective linearly higher result. Which was how I calc'd how much of my 'tested' chlorine I needed to add to my poo's volume, to get the rise I wanted...

Anyway, sorry...I'm long winded...I have a stoopid question:

I'm certain '1 PPM' means: One Part Per Million (all of the same size parts)
so...
how can the 'result' of the 10liter test be a 'PPM' value, when the basis for this method's ratio is 1 in 10,000...and not 1 in 1,000,000? The number will be the same but the decimal point is wrong...right?

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I think I just figured it out! (but I'm not deleting this...it took me 20 minutes to get this far...so I'm hunting for confirmation now...)

The 10 liter test result isn't a PPM value. It really is only a PP10,000th value.
But...Carl never "said" the test result would be in 'PPM'. The test is to determine the % concentration of the bleach being tested.
A % is a 1/100th value...and 10,000 is 1/100 of 1,000,000!
The DPD-FAS result really is a PPM value, of what's going on in the bucket. But...the ratio of bleach to water is jacked up by 100 times...and nobody told the FAS-DPD...and because of that 100x-ing the PPM number turns into a % number!
VERY CLEVER and damn easy!

Now I understand what giroup01's point is...Your test assumes a 1:1 relationship between PPM and % Sodium Hypochloride. He's saying that ratio isn't exactly 1:1, but that the PPM of chlorine available is slghtly lower...and that will fudge your results.
I see his point, purely...but, as I rambled on in that other thread...I'm testing my pool to +/- 0.5PPM resolution. I'm willing to bet that variation won't manifest enough error...at 'normal' % concentration values. I guess If I wanted to be a purist, I could just chuck in that 'factor' in the final PPM vs % result. I think I'll tinker with this...just for gags...