pH meter and the mysteries of pH

[BowserB]

I have the meter from TFTestkits.com, along with all the other stuff they sell. I have trouble with color matching, and since I generally have my FC at 6, the drop tests rarely get used. Over time, I've bought various calibration powders to mix and calibrate the meter, but recently in the process of discussing non-pool pH matters, I did some non pool pH testing and research with fairly unexpected results. This investigation started with a conversation about two recent pop-health fads: apple cider vinegar and baking soda, and a friend who mixes them with water as a daily potion. What, you ask? Yeah, me too.

Anyway, pure water has a pH of 7, as does distilled water immediately after distillation. However, distilled water absorbs CO2 from the air, and its pH drops, possibly even before it's bottled. Otherwise, why wouldn't you just use distilled water by itself to calibrate a pH meter? Maybe a sealed bottle of medical-grade distilled water (is there such a thing?) would come close to 7. ACV has a pH of around 2.75. Baking soda is 8.3. My potassium-softened tap water is 7.7, and my reverse osmosis drinking water comes in at 6.7. Water from a half bottle of distilled water that has been open for several months, says 6.0! And these domestic water tests I've reported here is from the TFTTestkits meter, but now I have doubts about the meter, since I've relied on calibration powders mixed with "distilled water" to calibrate. Clearly I need to go back to calibration liquids like sold by TFTTestkits.com, since who knows what the pH really is with powders added to mystery water pH.

Bottom line is I don't really know the pH of my pool water, do I?

 

[ajw22]

Bottom line is I don't really know the pH of my pool water, do I?

GIGO.

Do a drop pH drop test. Anywhere in the 7's is ok.

I have only used calibrating solutions with the pH meters I have used. I found the yellow pH meter TFT sells to get more inaccurate and lose calibration over time. I have gone to more expensive pH meters that seem to be more reliable.

 

[Msch99]

I bought a meter, but never use it anymore. Even if I am off on the color a bit, .2 doesn’t really matter much.

 

[scottts]

Bulb type pH meters don’t work with very low ion content water like RO or DI or distilled. My Apera unit had a note to that effect on the instructions.