Do you know why the pH of distilled water is more than 8?

[memari]

Do you know why the pH of distilled water is more than 8?

I have checked it in IRAN in National Genome Center and in Iranian Institute of Pasteur and

in Canada, in McGill University and in Quebec Genome center.

The pH of distilled water is near 8 and the pH of 18mega ohm water in 10.

is the CO2 of air is the cause?

[mchlbrmn]

CO2 would create carbonic acid in water, and shift the pH towards the acidic. I don't know the cause of your high pH. Pure water would have no buffering ability, so a trace of any contaminant in the water, or in the pH measurement, would throw off the number. Also, it may be difficult to measure accurately water with such low conductivity.

[Astarte]

I agree with mchlbrmn. Perfectly distilled water containing only H2O and its ions will have a pH of exactly 7. However, in the practice, you will never obtain this. Contact with the air will lead to acidification of the water because it has no buffering capacity. i did the maths on this during my phd to convince my PI it was not a good idea to used the distilled water from the lab to make coffee.
If you measure a high pH, I suspect this is due to the nature of the distillation process used that favors the removal of certain ions while leaving in others. Because distilled water is not buffered, even trace amounts of ions cause the ph to deviate a lot from the perfect 7 (ever tried to get the pH of an unbuffered solution just right? it is hell)

[mchlbrmn]

I think coffee would be fine from distilled water. As you said, it has no bufferring capacity, so the coffee would determine the pH. (But, if some dolt contaminated the faucet, or if Lab Safety caught you drinking from it, the result might not be good.)