pH reagent testing

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S

STRIEB

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Sep 13, 2016
7
Fishers
I am testing the pH in my pool using the R-0004 Taylor reagent. I initially (in about 10 seconds) get a results showing my pH is 7.5. However after about 20-30 seconds the color starts to turn to dark red and ultimately gets to purple…..I have never noticed this happening in the past. I have owned a pool for 15 years. I am closing my pool in 4 days and need to know if indicates that I have a problem….. thanks for your help.
 
Welcome to the forum.

What is your FC? The test is acting like the FC is near or above 10 ppm.
 
I have also taken my water to Leslie’s and they say the pH is 7.5 and had no idea why the reagent test was doing what I mentioned. I did the reagent test in front of them and they said: “ I have never seen that before”
 
STRIEB said:
FC is 5.1
Click to expand...
How are you testing FC? Looks like a Leslie's result. I suspect that your FC is actually higher which brings Marty's explanation back in.

Edit: Just saw that you already commented on that. You said you confirmed that with your own test. Was that FAS/DPD titration, just FAS, or OTO?
 
How old is the R-0004? Maybe Taylor's additives that remove the chlorine interference are not working anymore? Try adding a drop of R-0007 to remove the chlorine from your sample. It will change the pH, so don't do that to actually test for pH, I just want to see with this test if the drift disappears.
 

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That's odd. It's as if they have forgotten to put their chlorine interference remover into this batch of R-0004.

I usually test with a meter, but I just took a sample of my pool water that sits currently at FC 11ppm. My pH is around 7.8 right now, so I first added some acid demand drops to take pH down to about 7.4 to make a drift more visible and then added R-0004. Even though my FC is slightly above 10ppm, the test worked fine, no drift noticeable.

At FC 5ppm, your R-0004 should work absolutely fine, without any drift. I'd say there's something wrong with it.

As a work around, so you can close your pool with peace of mind, there is a trick to reduce the FC of a sample without changing the pH: Make a 1:1 dilution with distilled (or deionized) water - this is important, tap water doesn't work. Because distilled water has no Alkalinity (that's reason 1 why tap water doesn't work, tap water has Alkalinity), but your pool water has (which means that it is buffered), the dilution will not significantly change the pH of the sample, but it will half the chlorine (that's reason 2 why tap water doesn't work, tap water is usually chlorinated). Let's hope that your R-0004 can cope with FC 2.5ppm.

And then I'd order another bottle of R-0004.
 
This is a textbook example of a compromised reagent. I suggest (1) visiting the Taylor website for further information and (2) replacing your current R-0004 reagent with a new (different) batch. If the new reagent works properly, and you have no reason to believe that you caused a problem with the reagent, I would telephone Taylor and report the issue. If they screwed up, I'm sure their phone is ringing off the hook, by now. They will surely make good on the product.
 
Thanks for all of your help. I actually have 2 bottles of R-0004 because the person at the Leslie pool store suggest that my bottle might be old…turns out is doesn’t expire until June 2023….both bottles act the same.
 
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