Struggling with PH testing and conflicts

[midlifecrisis]

When I purchased my TF-100 Pro in February, I also purchased the PH meter. Since that time, I've been using it AND the drop test (comparator block with the Taylor R-0004 solution). I will ask my wife to spot me a color test on the drop test (because I struggle with red, even with four drops instead of five), and I've gotten where I can "get" within a couple tenths of a point. A couple of weeks ago, I noticed that my PH meter drifting and my trust in it waned a bit. Anyway... My dad actually had a new one he purchased a few weeks ago but hadn't used so I scored it.

It isn't the Apera, but I figured it would be worth a try. About 90 minutes ago, I calibrated it using the solution powder with distilled water (250ml per instructions); 7.00, 4.00, and the 10.01. Then, I used my Atlas Scientific liquid solutions of 4.00. 7.00, and 10.00 . The readings were spot on between powder solutions with the exception of the 10.00 solution and it was .01 high. Close enough. I tested back and forth a couple of time rinsing the probes between each test results were what they should be. I tested a sample of water from my pool with the meter and the results show 7.4. Here is the kicker, for me... When I tested with the drop test I was reading higher than 8 (obviously can't read it higher, but it was a "skosh" darker.

So, new meter, 7.4, drop test, 8... I asked my wife what she thought, and she came back with a "bit higher than 8". Since my PH solution is almost empty, I got my new bottle (purchased from TFtestkits during their March sale) and the results were identical.

Now I am not sure what to do or trust. Am I missing something? I really feel I need to trust the drop test solution but its hard to do when I tested and calibrated like I did. That's a huge difference.

Looking for some guidance...

 

[midlifecrisis]

P.S. I ditched the old meter. I calibrated it also with the same solution and it would seem to be on crack.

 

[Mdragger88]

Trust the drop test. Use a white background to look at the comparator.
Get ph into the 7’s & don’t sweat it.

 

[mgtfp]

Was your FC above 10? That would skew the drop test. Otherwise I'd trust the Taylor drop test result.

I generally don't have much confidence in cheap pH-meters.

 

[BDY]

I ditched the old meter and upgraded to an inexpensive Apera. Easy to calibrate and necessary as my FC is >10

Ph20 or ph60 are good ones

 

[ajw22]

Any pH in the 7s is ok.

Why are you sweating 0.1 differences?

Trash the yellow pH meter.

 

[duraleigh]

Well, I'll glom on with the drops test crowd. It is historically dependable and accurate enough for our purposes

 

[midlifecrisis]

Was your FC above 10? That would skew the drop test. Otherwise I'd trust the Taylor drop test result.

I generally don't have much confidence in cheap pH-meters.

It was actually 8, but that was my first though.

 

[mgtfp]

With FC 8, the drop test pH result is fine