ph testing connundrum

[PoolDiver]

Hi, everyone!

I'm stuck on a ph testing issue and I'm not sure how to proceed. The core of the problem is conflicting readings. This is for a plaster indoor pool with bromine chemistry (alas, due to a built-in hot tub), water @ 84F. The pool has been covered & unused for about 2 months. Normally, when balanced and unused, it can go for months without the chemistry getting out of whack.

- Measure 1: 7.5. This is done with Taylor K-2006 purchased August, 2014 from Amazon.
- Measure 2: 7.4. This is done with Taylor K-1004 purchased August, 2014 from Amazon.
- Measure 3: 7. This is done with Milwaukee MW-102 which pegs a 7ph Atlas reference liquid less than a year old at 7.05.

My gut tells me that the Milwaukee is right because of the reference liquid measurement. Those things are made for labs. However, both Taylor tests agree closely and also have relatively fresh chemicals.

The bigger question is, if I can't trust the Taylor ph tests, how can I trust their other tests? For example, both test kits read TA at 140 now while I normally keep it in the 100-110 range.

I'd appreciate some advice on how to proceed...

Thanks!

 

[JasonLion]

What is your current bromine level? High bromine levels could interfere with the PH test results.

 

[PoolDiver]

Bromine level is low: around 2.

 

[JasonLion]

Mystifying.

 

[PoolDiver]

Mystifying sums is up nicely. Any suggestions for things to try?

 

[Patrick_B]

Just because the meter reads 7.0 on the buffer doesn't mean it's right on the pool. Buffers are very easy for ph meters to read as they have few to no interference compounds in them. Being brutally honest with you, and please don't be insulted, but that isn't a great pH meter. Also, has it been calibrated to two or more points often and recently? Has the sensor been properly maintained and replaced in the last year if it isn't brand new?

All this matters because pH meters are very finicky and sometimes tricky. As a rule, only the more expensive models are consistent and reliable. Even these need constant and careful maintenance to stay dependable. You have two other sources that are nearly dead on with each other. Don't rely on the third that doesn't agree.

 

[pragmatic]

..Bingo on what Brushpup said!