effects of higher FC and PH testing

[miwitte]

I know that if FC gets too high then the PH numbers will be off. Question is are PH numbers the same at FC levels of 4, 6, 8 (all in range of my CYA of 50) I am seeing some PH bounce around over the last week or so from 7.4 to 7.7-7.8(not quite the color of 7.8 but not 7.6). I didn't record the FC when I did the testing so the FC could be between 4-8 which is where I try to keep it. I know my TA is low but it was recommended here to leave it be unless you are getting PH bounce. I wish there was a drop test for PH like all the other test we do , trying to look at a color is pretty subjective to lighting.

FC 8.0
CC 0.0
OCLT 0.0
CYA 50
PH 7.7
TA 60
CH 110

 

[tim5055]

It should have a minimal effect if any at all. As a color match test, the pH is a little subjective. But, don't fall in the trap that your pH needs to be exactly "X". It's better to keep it in a comfortable range, like 7.4 - 7.7 rather then fighting to keep it at exactly 7.5.

 

[duraleigh]

Question is are PH numbers the same at FC levels of 4, 6, 8

Yes.

 

[JoyfulNoise]

I don't mean to pile-on as the answers already given are correct; but let me just add to them. With an FC between 0-10ppm, the R-0004 reagent is designed to read correctly as it has a chemical formulation that neutralizes the chlorine in a way that doesn't change the pH. Between 10-20ppm FC, the formulation can't neutralize all of the chlorine in solution BUT the reaction of chlorine with phenol red is slow enough that even in that range you probably have 30sec or so before the color starts to change (chlorine causes the phenol red to turn into chlorphenol red which has a reddish-purple color at pH above 7.0). Above 20ppm FC, the reaction starts to happen too quickly to get an accurate reading and, above 25ppm, the phenol red will be completely compromised by the chlorine present.

So your pH fluctuations are due to something else in your testing, not your FC levels.

 

[Susiejax]

I don't mean to pile-on as the answers already given are correct; but let me just add to them. With an FC between 0-10ppm, the R-0004 reagent is designed to read correctly as it has a chemical formulation that neutralizes the chlorine in a way that doesn't change the pH. Between 10-20ppm FC, the formulation can't neutralize all of the chlorine in solution BUT the reaction of chlorine with phenol red is slow enough that even in that range you probably have 30sec or so before the color starts to change (chlorine causes the phenol red to turn into chlorphenol red which has a reddish-purple color at pH above 7.0). Above 20ppm FC, the reaction starts to happen too quickly to get an accurate reading and, above 25ppm, the phenol red will be completely compromised by the chlorine present.

So your pH fluctuations are due to something else in your testing, not your FC levels.

Thanks for this helpful info! I have to keep my FC pretty high because I am operating a high-CYA pool at the moment. Good to know exactly what is happening with the Phenol Red.

 

[Lykly]

JoyfulNoise: with C less than 10, do you still have a ~30 second time frame to read the ph? Just curious as sometimes I do the test and look to confirm again after I complete other tests.


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[tim5055]

JoyfulNoise: with C less than 10, do you still have a ~30 second time frame to read the ph? Just curious as sometimes I do the test and look to confirm again after I complete other tests.


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No, you have more than 30sec below 10FC. As Matt pointed out, the Taylor,solution contains a chlorine neutralizer good up to 10FC.

 

[JoyfulNoise]

There should be no waiting or letting test samples sit around. Just simply take your reading as soon as the sample is properly mixed and discard the solution once you're done. Any solution left to sit around would be considered invalid in my opinion. I test pH daily (or pretty close to that). The way I do it is too add my 5 drops of phenol red, invert twice or three times (gently!) to mix and then read the color. I usually stand in the shade under an awning but I put my hand holding the test vial out into the bright light. I then point the tube at one of my chase lounge chairs (which is bright white) and I read the color. It's very accurate that way and I always get the colors that I expect.

 

[Lykly]

Much the same way I do it, I usually stand in the shade and use a light colored background, normally a light colored cloud if available. You can normally tell when you have the background correct because all the colors make sense. Thanks for answering my question, even though I normally read it right away, I will sometime set it down while I perform other tests and then look at it again to see if the result has changed. I do understand though, that the initial test result is the valid one.


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