Calibrating PH Meter Without Buffer Solution

[Saisonator]

I plan to brew a Malt Miller Winter Witt tomorrow, all acid and other additions calculated but for a change I will PH test my wort.
My deionised water has gone from 4.5 to 6.5 PH in the last 8 months so I'm guessing it will be no good to use with my buffer powders.
After a search online I decided to give two things a try to calibrate my PH meter (cheap yellow Chinese type)
First vinegar is PH 2.4 whether Malt or distilled and bottled water has the PH printed on the side, probably should not be too old to match the figure.
So I first dipped the PH meter in the vinegar and calibrated it to 2.4, the checked it with the bottled water and it read 6.48, the bottle has the figure 6.5 so near enough.
I think the meter will be accurate enough for checking my wort tomorrow, unless someone can correct me.

 

[strange-steve]

It's very difficult (read pointless) trying to take a pH reading of very low mineral water such as distilled, RO or deionised because it has almost zero buffering capacity. My point being your DI water is probably fine, and your pH meter couldn't tell you if it wasn't anyway.

I would say make up the buffering solution with the DI water and use that. Household items like vinegar are not necessarily going to be pH stable so your vinegar might not actually be 2.4. From what I understand, Coca Cola does have a rather steady pH of 2.6 though when degassed.

 

[Saisonator]

Interested to hear my distilled water is still of use, I have about 4 litres of it.
Cheers Steve