TA suddenly reading many times higher on Taylor drop test

[lightning_phoenix]

Anyone seen this before? TA was reading in the 70-90 range. After one night its now reading 650 on Taylor drop tests. Diluting half with distilled water reads around half that (350). TA measured on Hanna colorimetric test reads 110 and reads 24 diluted 9:1 with distilled water. TA on test strips (ugh!) reads somewhere between 40 and 120, impossible to tell exactly (of course, I don’t use test strips except as a last resort)

Hard to think the Taylor reagents suddenly went bad in a single night. They’re stored inside in a cabinet in the dark at 72F.

For context, pH is 7.5, TC & FC are at 3.5, CH is around 400. Pool is 2 years old.

Fill water TA reads at 120ppm on the same Taylor drop test.

 

[Texas Splash]

fter one night its now reading 650 on Taylor drop tests.

What? That's very odd indeed and almost seems impossible. Which Taylor kit are you using? Can you explain the testing method and math you used for that test?

By the way, good morning and welcome to TFP!

Pool Care Basics Archives

Your one-stop shop for all things TFP to include: ABCs of Water Chemistry, Recommended Chemicals/Levels, Test Kits, Troubleshooting, and much more!

www.troublefreepool.com

 

[lightning_phoenix]

Test Kit: Taylor K-2006

Testing method:
- 25ml sample in large tube
- Place on on Taylor SpeedStir base, add magnet stir “pill”
- 2 drops R-0007 (thiosulfate)
- 5 drops R-0008 (TA indicator)
- add R-0009 (sulfuric acid) dropwise til color changes from green to red, multiply count x10ppm
I’ve done this test dozens of times in the past including the prior night. There’s nothing special about this test run other than the crazy results. I repeated the test several times out of disbelief but each showed the same result.

Reconfirmed again with 10ml sample, 1 drop R-0007, 3 drops R-0008, and then R-0009 dropwise til color change, multiplied drop count x25ppm which yielded the same results as the initial test.

Re-tested per second method (10ml sample but 5ml distilled water and 5ml sample water), with results at 50% of original test.


Using Hanna HI775 as a cross reference (not my preferred method), the testing method:

- Meter on
- Fill cuvette to 10ml line with sample
- Add one drop HI93755-53 (chlorine remover) to unreacted sample
- Place cuvette in meter, close cap, press button to zero meter against unreacted sample
- Remove cuvette from meter, add 1ml of HI775S reagent, invert 5x to mix
- Replace cuvette in meter, press button

Per above test method, with 10ml pool water sample, meter reads 110ppm.

Also prior to above, I checked the calibration of Hanna meter using the HI775-11 reference standards kit. The reference standard metered in at 100ppm (actual standard value is 101ppm, +/-10ppm). So right on the money.

Using the Hanna meter with 1ml pool water sample mixed with 9ml distilled water in the cuvette, the meter reads 24ppm (+/- 10ppm). So mostly consistent with the full-strength measurement although probably not super accurate in the low end of the measurement range.

 

[Texas Splash]

I've never heard of a reagent issue or such a wide disparity of the TA test in a matter of 24 hrs or so. Let's ask for some reinforcements on this question with @JoyfulNoise and @Leebo.

 

[lightning_phoenix]

Update: Replaced the sulfuric acid with a new bottle and the Taylor test is producing sane results again.